Co-reporter:Chih-Hao Hsu, Kan Yue, Jing Wang, Xue-Hui Dong, Yanfeng Xia, Zhang Jiang, Edwin L. Thomas, and Stephen Z. D. Cheng
Macromolecules September 26, 2017 Volume 50(Issue 18) pp:7282-7282
Publication Date(Web):September 11, 2017
DOI:10.1021/acs.macromol.7b01598
Controlling self-assembled nanostructures in thin films allows the bottom-up fabrication of ordered nanoscale patterns. Here we report the unique thickness-dependent phase behavior in thin films of a bolaform-like giant surfactant, which consists of butyl- and hydroxyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS and DPOSS) cages telechelically located at the chain ends of a polystyrene (PS) chain with 28 repeating monomers on average. In the bulk, BPOSS-PS28-DPOSS forms a double gyroid (DG) phase. Both grazing incidence small-angle X-ray scattering and transmission electron microscopy techniques are combined to elucidate the thin film structures. Interestingly, films with thicknesses thinner than 200 nm exhibit an irreversible phase transition from hexagonal perforated layer (HPL) to compressed hexagonally packed cylinders (c-HEX) at 130 °C, while films with thickness larger than 200 nm show an irreversible transition from HPL to DG at 200 °C. The thickness-controlled transition pathway suggests possibilities to obtain diverse patterns via thin film self-assembly.
Co-reporter:Bernard Lotz, Toshikazu Miyoshi, and Stephen Z. D. Cheng
Macromolecules August 22, 2017 Volume 50(Issue 16) pp:5995-5995
Publication Date(Web):August 22, 2017
DOI:10.1021/acs.macromol.7b00907
Analyzing and understanding the structure and morphology of crystalline polymers has been and remains to be a major challenge. Some of the issues have resisted analyses for decades. The present account illustrates how individual contributions help build a body of knowledge that must cover length scales ranging from submolecular features to morphology and correlates them with bulk properties. Emphasis is put on structures and morphologies as formed spontaneously. Possible extension of the research area to connected fields is illustrated with a development on supramolecular crystals.
Co-reporter:Guang-Zhong Yin;Wen-Bin Zhang;Stephen Z.D. Cheng
Science China Chemistry 2017 Volume 60( Issue 3) pp:338-352
Publication Date(Web):2017 March
DOI:10.1007/s11426-016-0436-x
This feature article focuses on the recent development of giant molecules, which has emerged at the interface among chemistry, physics, and bio-science. Their molecular designs are inspired by natural polymers like proteins and are modularly constructed from molecular nanoparticle building blocks via sequential “click” chemistry. Most important molecular parameters such as topology, composition, and molecular weight can be precisely controlled. Their hierarchical assembly reveals many features reminiscent of both small molecules and proteins yet unusual for conventional synthetic polymers. These features are summarized and compared along with synthetic polymers and proteins. Specifically, examples are given in each category of giant molecules to illustrate the characteristics of their hierarchical assembly across different length, time and energy scales. The idea of “artificial domain” is presented in analogy to the structural domains in proteins. By doing so, we aim to develop a rational and modular approach toward functional materials. The factors that dominate the materials functions are discussed with respect to the precision and dynamics of the assembly. The complexity of structure-function relationship is acknowledged, which suggests that there is still a long way to go toward the convergence of synthetic polymers and biopolymers.
Co-reporter:Kan Yue, Chang Liu, Mingjun Huang, Jiahao Huang, Zhe Zhou, Kan Wu, Hao Liu, Zhiwei Lin, An-Chang Shi, Wen-Bin Zhang, and Stephen Z. D. Cheng
Macromolecules 2017 Volume 50(Issue 1) pp:
Publication Date(Web):December 20, 2016
DOI:10.1021/acs.macromol.6b02446
We report a remarkable sensitivity of self-assembled structures of giant surfactants on their chemical compositions and molecular topology, which facilitate the engineering of various nanophase-separated structures with sub-10 nm feature sizes. Two classes of giant surfactants composed of various functionalized polyhedral oligomeric silsesquioxane (POSS) heads tethered with one or two polystyrene (PS) tails were efficiently prepared from common precursors of vinyl-substituted POSS–PS conjugates via one-step “thiol–ene” postpolymerization functionalization. With identical molecular weights of the PS tails, the resulting giant surfactants exhibited distinct highly ordered phases, as evidenced by small-angle X-ray scattering and transmission electron microscopy observations. Moreover, comparison between the topological isomers revealed that the self-assembled structures are also highly sensitive to molecular topology. Introduction of two PS tails with half-length not only shifted the boundaries between different ordered phases but also altered the packing configurations of the functional POSS cages, leading to further reduced feature sizes of the self-assembled nanodomains. Interestingly, a lower order–disorder transition temperature was also observed in the fluorinated F13POSS tethered with two PS17 tails, compared to its topological isomer composed of F13POSS tethered with one PS35 tail, indicating that the topological effect also existed in phase transition behaviors. These results provide insights to rationally design and precisely tailor self-assembled structures by controlling both primary chemical compositions and molecular topology in POSS-based giant surfactants.
Co-reporter:Wen-Bin Zhang;Xia-Ling Wu;Guang-Zhong Yin;Yu Shao
Materials Horizons (2014-Present) 2017 vol. 4(Issue 2) pp:117-132
Publication Date(Web):2017/03/06
DOI:10.1039/C6MH00448B
Synthetic polymers are still considered as primitive as compared to the sophisticated polymeric machines like proteins. There is so much that synthetic materials can learn from proteins. This review discusses an emerging class of precision macromolecules called “giant molecules” in the context of materials genome initiative, as a tribute to the workhorse of Nature – the proteins. In protein science, modular protein domains can be tuned and combined in different ways to create new and versatile functions. Inspired by the “domain” concept, we draw an analogy between protein domains and molecular nanoparticles with the hope of developing “artificial domains” for synthetic polymers. Giant molecules are polymers built on such artificial domains. The two categories are then discussed in parallel with respect to their specific types, how they can be engineered, and how they would assemble hierarchically. Indeed, giant molecules share many features common with proteins and exhibit many unconventional hierarchically assembled structures and intriguing phase behaviors at different length, energy and time scales. The functions of giant molecules and their relation to the assembled hierarchical structures are under intense investigation, which shall pave the way to developing a modular and rational approach for advanced materials. Under the materials genome initiative, the field of giant molecules calls for an even closer, more dynamic and creative joint endeavor among chemistry, physics, and biology.
Co-reporter:Wei Zhang;Xinlin Lu;Jialin Mao;Chih-Hao Hsu;Gaoyan Mu;Mingjun Huang;Qingyun Guo;Hao Liu; Chrys Wesdemiotis;Tao Li; Wen-Bin Zhang; Yiwen Li; Stephen Z. D. Cheng
Angewandte Chemie 2017 Volume 129(Issue 47) pp:15210-15215
Publication Date(Web):2017/11/20
DOI:10.1002/ange.201709354
AbstractAlthough controlling the primary structure of synthetic polymers is itself a great challenge, the potential of sequence control for tailoring hierarchical structures remains to be exploited, especially in the creation of new and unconventional phases. A series of model amphiphilic chain-like giant molecules was designed and synthesized by interconnecting both hydrophobic and hydrophilic molecular nanoparticles in precisely defined sequence and composition to investigate their sequence-dependent phase structures. Not only compositional variation changed the self-assembled supramolecular phases, but also specific sequences induce unconventional phase formation, including Frank–Kasper phases. The formation mechanism was attributed to the conformational change driven by the collective hydrogen bonding and the sequence-mandated topology of the molecules. These results show that sequence control in synthetic polymers can have a dramatic impact on polymer properties and self-assembly.
Co-reporter:Wei Zhang;Xinlin Lu;Jialin Mao;Chih-Hao Hsu;Gaoyan Mu;Mingjun Huang;Qingyun Guo;Hao Liu; Chrys Wesdemiotis;Tao Li; Wen-Bin Zhang; Yiwen Li; Stephen Z. D. Cheng
Angewandte Chemie International Edition 2017 Volume 56(Issue 47) pp:15014-15019
Publication Date(Web):2017/11/20
DOI:10.1002/anie.201709354
AbstractAlthough controlling the primary structure of synthetic polymers is itself a great challenge, the potential of sequence control for tailoring hierarchical structures remains to be exploited, especially in the creation of new and unconventional phases. A series of model amphiphilic chain-like giant molecules was designed and synthesized by interconnecting both hydrophobic and hydrophilic molecular nanoparticles in precisely defined sequence and composition to investigate their sequence-dependent phase structures. Not only compositional variation changed the self-assembled supramolecular phases, but also specific sequences induce unconventional phase formation, including Frank–Kasper phases. The formation mechanism was attributed to the conformational change driven by the collective hydrogen bonding and the sequence-mandated topology of the molecules. These results show that sequence control in synthetic polymers can have a dramatic impact on polymer properties and self-assembly.
Co-reporter:Yiwen Li, Xue-Hui Dong, Yuan Zou, Zhao Wang, Kan Yue, Mingjun Huang, Hao Liu, Xueyan Feng, Zhiwei Lin, Wei Zhang, Wen-Bin Zhang, Stephen Z.D. Cheng
Polymer 2017 Volume 125(Volume 125) pp:
Publication Date(Web):8 September 2017
DOI:10.1016/j.polymer.2017.08.008
•Feature article (177 references) focusing on the use of “click” reaction to prepare POSS-based hybrid materials.•Emphasis on POSS-based “clickable” building blocks and related hybrids construction strategies.•Discussion on their rational design, facile synthesis, and tunable properties.•Perspective on “click” fabrications of POSS-based functional materials with diverse applications.The continuous demand for novel hybrid materials in specific technological applications inspires people to develop new synthetic strategies in a modular and efficient way. In the recent years, extensive efforts have been devoted to using polyhedral oligomeric silsesquioxane (POSS) to construct multifunctional nanohybrids and nanocomposites with tunable hierarchical structures and unparalleled properties. The shape-persistent nanostructure and diverse surface chemistry make those nanocaged materials ideal building blocks for such purposes. Functionalization of POSS cages are further facilitated by the introduction of “click” chemistry at the beginning of this century. “Click” reactions include several kinds of selective and orthogonal chemical ligations with high efficiency under mild reaction conditions. The concept has generated real stimulus not only in elegantly preparing materials of choice, but in making the leap from laboratory to industrial scale-up of POSS-based hybrid materials as well.Download high-res image (271KB)Download full-size image
Co-reporter:Joseph X. Zheng, Ryan M. Van Horn, Stephen Z.D. Cheng
Polymer 2017 Volume 116(Volume 116) pp:
Publication Date(Web):5 May 2017
DOI:10.1016/j.polymer.2017.02.091
•A model of “mobile” polymer brushes tethered on a polymer single crystal has been proposed based on the Flory treatment.•The scaling relation between polymer chain dimension (L) and the polymer chain length (r) has been shown to lie in between the polymer solution and polymer brushes cases: L ∼ r2/3 for a poor solvent, L ∼ r3/4 for a theta solvent and L ∼ r4/5 for a good solvent.•This model is able to describe many nano-phase separated interfaces in polymers.“Mobile” polymer brushes with self-adjustable tethering density can be found in the single crystals of amorphous-crystalline diblock copolymers in the thermodynamically stable state. In such a system, the amorphous blocks form polymer brushes on the surface of the single crystal of the crystalline blocks. Different from the common polymer brushes with fixed tethering density, of which polymers are attached either chemically or physically on a substrate, the polymer brushes tethered on the single crystal are “smart” and partially release the highly stretched conformation by “telling” the crystalline blocks to provide more surface area via forming higher folded chain single crystals. Such a polymer brushes system is treated theoretically using the Flory approximation. Thicknesses of the amorphous polymer brush layer (La) and the single crystal lamellae (Lc) are found to have different scaling relations with the degree of polymerization of the amorphous block (ra) in different types of solvents. The amorphous layer thickness, La, is proportional to the 2/3 power of ra in a poor solvent for the amorphous blocks, the 3/4 power in theta solvent, and the 4/5 power in good solvent. The scaled powers between La and ra of the “mobile” polymer brushes are all weaker than the normal polymer brushes, which scales with ra to the first power, indicating the partial releasing of the stretched nature. The crystal thickness, Lc, is proportional to the −1/3 power of ra in poor solvent for the amorphous blocks, the −1/2 power in theta solvent, and the −3/5 power in good solvent, clearly indicating that a folded chain single crystal possesses a larger number of folds at a large ra to facilitate the crowding of the amorphous chains on the surface.Download high-res image (279KB)Download full-size image
Co-reporter:Yang Chu, Wei Zhang, Xinlin Lu, Gaoyan Mu, Baofang Zhang, Yiwen Li, Stephen Z. D. Cheng and Tianbo Liu
Chemical Communications 2016 vol. 52(Issue 56) pp:8687-8690
Publication Date(Web):15 Jun 2016
DOI:10.1039/C6CC04567G
A series of multi-headed giant surfactants based on polystyrene (PS)-polyhedral oligomeric silsesquioxane(s) (POSS) conjugates, with a different number and topology of POSS heads, are found to self-assemble into different supramolecular structures including vesicles, cylindrical and spherical micelles in H2O/DMF mixed solvents. The transitions among different morphologies can be rationally controlled by tuning the number and topology of POSS heads, as well as the macromolecular concentration.
Co-reporter:Wei Zhang, Mingjun Huang, Hao Su, Siyu Zhang, Kan Yue, Xue-Hui Dong, Xiaopeng Li, Hao Liu, Shuo Zhang, Chrys Wesdemiotis, Bernard Lotz, Wen-Bin Zhang, Yiwen Li, and Stephen Z. D. Cheng
ACS Central Science 2016 Volume 2(Issue 1) pp:48
Publication Date(Web):January 27, 2016
DOI:10.1021/acscentsci.5b00385
Herein we introduce a unique synthetic methodology to prepare a library of giant molecules with multiple, precisely arranged nano building blocks, and illustrate the influence of minute structural differences on their self-assembly behaviors. The T8 polyhedral oligomeric silsesquioxane (POSS) nanoparticles are orthogonally functionalized and sequentially attached onto the end of a hydrophobic polymer chain in either linear or branched configuration. The heterogeneity of primary chemical structure in terms of composition, surface functionality, sequence, and topology can be precisely controlled and is reflected in the self-assembled supramolecular structures of these giant molecules in the condensed state. This strategy offers promising opportunities to manipulate the hierarchical heterogeneities of giant molecules via precise and modular assemblies of various nano building blocks.
Co-reporter:Chih-Hao Hsu, Xue-Hui Dong, Zhiwei Lin, Bo Ni, Pengtao Lu, Zhang Jiang, Ding Tian, An-Chang Shi, Edwin L. Thomas, and Stephen Z. D. Cheng
ACS Nano 2016 Volume 10(Issue 1) pp:919
Publication Date(Web):December 1, 2015
DOI:10.1021/acsnano.5b06038
The self-assembly behavior of specifically designed giant surfactants is systematically studied in thin films using grazing incidence X-ray scattering and transmission electron microscopy, focusing on the effects of molecular nanoparticle (MNP) functionalities and molecular architectures on nanostructure formation. Two MNPs with different surface functionalities, i.e., hydrophilic carboxylic acid functionalized [60]fullerene (AC60) and omniphobic fluorinated polyhedral oligomeric silsesquioxane (FPOSS), are utilized as the head portions of the giant surfactants. By covalently tethering these functional MNPs onto the end point or junction point of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer, linear and star-like giant surfactants with different molecular architectures are constructed. With fixed length of the PEO block, changing the molecular weight of the PS block leads to the formation of various ordered phases and phase transitions. Due to the distinct affinity, the AC60-based and FPOSS-based giant surfactants form two- or three-component morphologies, respectively. A stretching parameter for the PS block is introduced to characterize the PS chain conformation in the different morphologies. The highly diverse self-assembled nanostructures with high etch resistance between components in small dimensions obtained from the giant surfactant thin films suggest that these macromolecules could provide a promising and robust platform for nanolithography applications.Keywords: molecular architecture; nanoparticles; self-assembly; surface functionality; thin film;
Co-reporter:Hao Liu, Jiancheng Luo, Wenpeng Shan, Dong Guo, Jing Wang, Chih-Hao Hsu, Mingjun Huang, Wei Zhang, Bernard Lotz, Wen-Bin Zhang, Tianbo Liu, Kan Yue, and Stephen Z. D. Cheng
ACS Nano 2016 Volume 10(Issue 7) pp:6585
Publication Date(Web):June 23, 2016
DOI:10.1021/acsnano.6b01336
The ability to manipulate self-assembly of molecular building blocks is the key to achieving precise “bottom-up” fabrications of desired nanostructures. Herein, we report a rational design, facile synthesis, and self-assembly of a series of molecular Janus particles (MJPs) constructed by chemically linking α-Keggin-type polyoxometalate (POM) nanoclusters with functionalized polyhedral oligomeric silsesquioxane (POSS) cages. Diverse nanostructures were obtained by tuning secondary interactions among the building blocks and solvents via three factors: solvent polarity, surface functionality of POSS derivatives, and molecular topology. Self-assembled morphologies of KPOM-BPOSS (B denotes isobutyl groups) were found dependent on solvent polarity. In acetonitrile/water mixtures with a high dielectric constant, colloidal nanoparticles with nanophase-separated internal lamellar structures quickly formed, which gradually turned into one-dimensional nanobelt crystals upon aging, while stacked crystalline lamellae were dominantly observed in less polar methanol/chloroform solutions. When the crystallizable BPOSS was replaced with noncrystallizable cyclohexyl-functionalized CPOSS, the resulting KPOM-CPOSS also formed colloidal spheres; however, it failed to further evolve into crystalline nanobelt structures. In less polar solvents, KPOM-CPOSS crystallized into isolated two-dimensional nanosheets, which were composed of two inner crystalline layers of Keggin POM covered by two monolayers of amorphous CPOSS. In contrast, self-assembly of KPOM-2BPOSS was dominated by crystallization of the BPOSS cages, which was hardly sensitive to solvent polarity. The BPOSS cages formed the crystalline inner bilayer, sandwiched by two outer layers of Keggin POM clusters. These results illustrate a rational strategy to purposely fabricate self-assembled nanostructures with diverse dimensionality from MJPs with controlled molecular composition and topology.Keywords: Janus particles; nanobelts; nanosheets; polyoxometalates; self-assembly
Co-reporter:Chang Liu;Kan Yue;Xuesheng Yan;Jing Wang;Hao Liu;Zaihong Guo;Jiahao Huang;Ryan L. Marson;Jinlin He;Zhe Zhou;Kan Wu;Mingjun Huang;Wei Zhang;Peihong Ni;Chrys Wesdemiotis;Wen-Bin Zhang;Sharon C. Glotzer
PNAS 2016 Volume 113 (Issue 50 ) pp:14195-14200
Publication Date(Web):2016-12-13
DOI:10.1073/pnas.1609422113
Frank–Kasper (F-K) and quasicrystal phases were originally identified in metal alloys and only sporadically reported in soft
materials. These unconventional sphere-packing schemes open up possibilities to design materials with different properties.
The challenge in soft materials is how to correlate complex phases built from spheres with the tunable parameters of chemical
composition and molecular architecture. Here, we report a complete sequence of various highly ordered mesophases by the self-assembly
of specifically designed and synthesized giant surfactants, which are conjugates of hydrophilic polyhedral oligomeric silsesquioxane
cages tethered with hydrophobic polystyrene tails. We show that the occurrence of these mesophases results from nanophase
separation between the heads and tails and thus is critically dependent on molecular geometry. Variations in molecular geometry
achieved by changing the number of tails from one to four not only shift compositional phase boundaries but also stabilize
F-K and quasicrystal phases in regions where simple phases of spheroidal micelles are typically observed. These complex self-assembled
nanostructures have been identified by combining X-ray scattering techniques and real-space electron microscopy images. Brownian
dynamics simulations based on a simplified molecular model confirm the architecture-induced sequence of phases. Our results
demonstrate the critical role of molecular architecture in dictating the formation of supramolecular crystals with “soft”
spheroidal motifs and provide guidelines to the design of unconventional self-assembled nanostructures.
Co-reporter:Bo Ni; Mingjun Huang; Ziran Chen; Yingchao Chen; Chih-Hao Hsu; Yiwen Li; Darrin Pochan; Wen-Bin Zhang; Stephen Z. D. Cheng;Xue-Hui Dong
Journal of the American Chemical Society 2015 Volume 137(Issue 4) pp:1392-1395
Publication Date(Web):January 15, 2015
DOI:10.1021/ja511694a
We report the solution self-assembly of an ABC block terpolymer consisting of a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer tail tethered to a fluorinated polyhedral oligomeric silsesquioxane (FPOSS) cage in 1,4-dioxane/water. With increasing water content, abundant unconventional morphologies, including circular cylinders, two-dimensional hexagonally patterned colloidal nanosheets, and laterally patterned vesicles, are sequentially observed. The formation of toroids is dominated by two competing free energies: the end-cap energy of cylinders and the bending energy to form the circular structures. Incorporating the superhydrophobic FPOSS cages enhances the end-cap energy and promotes toroid formation. Lateral aggregation and fusion of the cylinders results in primitive nanosheets that are stabilized by the thicker rims to partially release the rim-cap energy. Rearrangement of the parallel-aligned FPOSS cylindrical cores generates hexagonally patterned nanosheets. Further increasing the water content induces the formation of vesicles with nanopatterned walls.
Co-reporter:Yiwen Li, Hao Su, Xueyan Feng, Kan Yue, Zhao Wang, Zhiwei Lin, Xiulin Zhu, Qiang Fu, Zhengbiao Zhang, Stephen Z. D. Cheng and Wen-Bin Zhang
Polymer Chemistry 2015 vol. 6(Issue 5) pp:827-837
Publication Date(Web):27 Oct 2014
DOI:10.1039/C4PY01360C
The combined utilization of chemoselective “click” chemistry allows for the preparation of well-defined macromolecules with complex compositions and architectures. In this article, we employed the sequential “click” strategy to further expand the scope of synthetically available giant molecules by precisely constructing new giant surfactants based on polyhedral oligomeric silsesquioxane (POSS) tethered cyclic polymers. The general synthetic approach involves sequentially performed strain-promoted azide–alkyne cycloaddition (SPAAC) as a method for bimolecular homobifunctional ring closure, copper-catalyzed azide–alkyne cycloaddition (CuAAC) for POSS-polymer conjugation, and thiol–Michael/thiol–ene reactions for POSS surface functionalization. Specifically, a cyclic polymer tethered with two POSS cages of distinct surface chemistry at different locations of the chain has been prepared. This work promises to afford numerous cyclic polymers-based giant surfactants with diverse structural variations for further investigation on unexpected physical properties.
Co-reporter:Zhiwei Lin, Pengtao Lu, Chih-Hao Hsu, Jian Sun, Yangbin Zhou, Mingjun Huang, Kan Yue, Bo Ni, Xue-Hui Dong, Xiaochen Li, Wen-Bin Zhang, Xinfei Yu, and Stephen Z. D. Cheng
Macromolecules 2015 Volume 48(Issue 16) pp:5496-5503
Publication Date(Web):August 6, 2015
DOI:10.1021/acs.macromol.5b00741
Phase behaviors of two series of giant surfactants consisting of a hydrophilic [60]fullerene (AC60) molecular nanoparticle (MNP) tethered to a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) block copolymer were investigated. The physical location of AC60 MNP was specifically designed to be at the end of the PS block (AC60-PS-PEO) or at the junction point [PS-(AC60)-PEO] between the PS and PEO blocks. Self-assemblies of these two series of giant surfactants in the bulk revealed that the incorporation of AC60 MNPs leads to nanophase separation of originally disordered PS-b-PEO block copolymers having their block lengths shorter than the limiting value for the nanophase separation in the PS-b-PEO precursors. Based on small-angle X-ray scattering and transmission electron microscopy results, three ordered nanostructures were observed in these two series of giant surfactants, including lamellae, double gyroids, and cylinders, all of which possess domain sizes smaller than 10 nm. Two pairs of topological isomers, AC60-PS50-PEO45 and PS50-(AC60)-PEO45 as well as AC60-PS78-PEO45 and PS78-(AC60)-PEO45, were explicitly investigated to reveal the topological effect on self-assembly behaviors of these giant surfactants. The results provided evidence of the physical location and distribution of the AC60 MNPs within the nanophase-separated domains and demonstrated abilities to stabilize the different structures via topological variations. This study thus affords an efficient and practical strategy for the design and preparation of giant surfactants to construct ordered nanostructures for technologically relevant applications.
Co-reporter:Xue-Hui Dong, Bo Ni, Mingjun Huang, Chih-Hao Hsu, Ziran Chen, Zhiwei Lin, Wen-Bin Zhang, An-Chang Shi, and Stephen Z. D. Cheng
Macromolecules 2015 Volume 48(Issue 19) pp:7172-7179
Publication Date(Web):September 18, 2015
DOI:10.1021/acs.macromol.5b01661
The self-assembly behaviors of fluorinated polyhedral oligomeric silsesquioxane (FPOSS)-based giant surfactants, consisting of an FPOSS cage and a polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer tail, are studied in the bulk. The tethering point of the FPOSS cage on the PS-b-PEO diblock copolymer chain can be controlled precisely either at the end of the PS block or the junction point between the PS and PEO blocks, resulting in topological isomer pairs with almost identical chemical compositions but different architectures. Phase separation between the FPOSS head and the block copolymer tail creates a spatially confined environment for the PS-b-PEO component, which are uniformly end- or junction-point-immobilized on the FPOSS layer, providing a unique model system to study phase behaviors and chain conformation of tethered diblock copolymer in the condensed state. The polymer tails are highly stretched because the cross-sectional area of FPOSS head is smaller than that of the unperturbed block copolymer tail, which facilitates further phase separation between the low molecular weight PS and PEO blocks and leads to the formation of hierarchical lamellar structures among three mutually immiscible components.
Co-reporter:Panchao Yin, Zhiwei Lin, Jiayingzi Wu, Chih-Hao Hsu, Xinyue Chen, Jing Zhou, Pengtao Lu, Seyed Ali Eghtesadi, Xinfei Yu, Stephen Z. D. Cheng, and Tianbo Liu
Macromolecules 2015 Volume 48(Issue 3) pp:725-731
Publication Date(Web):January 16, 2015
DOI:10.1021/ma5022314
Fullerene molecule covalently functionalized with 12 carboxylic acid groups on its periphery was synthesized, and its solution behavior was explored. The functionalized fullerene molecules behave as hydrophilic macroions in polar solvents by showing strong attractions with each other mediated from their counterions and consequently self-assembling into single-layer, hollow, spherical blackberry-type structures in solvents with moderate polarity. The fullerene molecules are not touching with each other in the assemblies, and the assembly size can be tuned by changing the polarity of the solvents. More importantly, the transition between the self-assembly and the disassembly of the macroions can be easily achieved by changing temperature. The discovery confirms that the semirigid clusters demonstrate the unique solution behavior of macroions and open up a new way to assemble fullerene into functional materials and devices.
Co-reporter:Mingjun Huang;Jing Wang;Xuehui Dong;Chih-Hao Hsu;Yiwen Li;Takuzo Aida;Wei Zhang;Shan Mei;Kan Yue;Mingxuan Li;Hao Liu;Wen-Bin Zhang
Science 2015 Volume 348(Issue 6233) pp:
Publication Date(Web):
DOI:10.1126/science.aaa2421
Creating unusual nanostructures
Self-assembly often occurs when dissimilar molecular fragments are forced together by covalent bonding. Surfactants or block copolymers are two common examples. Huang et al. grafted four different nanoparticles, based on polyhedral oligomeric silsesquioxanes with slightly different compositions, onto a single tetrahedal core (see the Perspective by Yang). Depending on the type of nanoparticle, they assembled into a range of defined, ordered supramolecular lattices similar to a range of metal alloys. These include phases that have higher coordination numbers than usually found in the packing of spherical objects.
Science, this issue p. 424; see also p. 396
Co-reporter:Hao Liu ; Chih-Hao Hsu ; Zhiwei Lin ; Wenpeng Shan ; Jing Wang ; Jing Jiang ; Mingjun Huang ; Bernard Lotz ; Xinfei Yu ; Wen-Bin Zhang ; Kan Yue
Journal of the American Chemical Society 2014 Volume 136(Issue 30) pp:10691-10699
Publication Date(Web):July 9, 2014
DOI:10.1021/ja504497h
This paper describes a rational strategy to obtain self-assembled two-dimensional (2D) nanocrystals with definite and uniform thickness from a series of molecular Janus particles based on molecular nanoparticles (MNPs). MNPs are 3D framework with rigid shapes. Three different types of MNPs based on derivatives of polyhedral oligomeric silsesquioxane (POSS), [60]fullerene (C60), and Lindqvist-type polyoxometalate (POM) are used as building blocks to construct these amphiphilic molecular Janus particles by covalently connecting hydrophobic crystalline BPOSS with a charged hydrophilic MNP. The formation of 2D nanocrystals with an exact thickness of double layers of molecules is driven by directional crystallization of the BPOSS MNP and controlled by various factors such as solvent polarity, number of counterions, and sizes of the MNPs. Strong solvating interactions of the ionic MNPs in polar solvents (e.g., acetonitrile and dimethylformamide) are crucial to provide repulsive interactions between the charged outlying ionic MNPs and suppress further aggregation along the layer normal direction. The number of counterions per molecule plays a major role in determining the self-assembled morphologies. Size matching of the hydrophobic and ionic MNPs is another critical factor in the formation of 2D nanocrystals. Self-assembly of rationally designed molecular Janus particles provides a unique “bottom-up” strategy to engineer 2D nanostructures.
Co-reporter:Yiwen Li, Kai Guo, Hao Su, Xiaopeng Li, Xueyan Feng, Zhao Wang, Wei Zhang, Sunsheng Zhu, Chrys Wesdemiotis, Stephen Z. D. Cheng and Wen-Bin Zhang
Chemical Science 2014 vol. 5(Issue 3) pp:1046-1053
Publication Date(Web):18 Nov 2013
DOI:10.1039/C3SC52718B
The convenient synthesis of nano-building blocks with strategically placed functional groups constitutes a fundamental challenge in nano-science. Here, we describe the facile preparation of a library of mono- and di-functional (containing three isomers) polyhedral oligomeric silsesquioxane (POSS) building blocks with different symmetries (C3v, C2v, and D3d) using thiol-ene chemistry. The method is straightforward and general, possessing many advantages including minimum set-up, simple work-up, and a short reaction time (about 0.5 h). It facilitates the precise introduction of a large variety of functional groups to desired sites of the POSS cage. The yields of the monoadducts increase significantly using stoichiometric amounts of bulky ligands. Regio-selective di-functionalization of the POSS cage was also attempted using bulky thiol ligands, such as a thiol-functionalized POSS. Electrospray ionization (ESI) mass spectrometry coupled with travelling wave ion mobility (TWIM) separation revealed that the majority of diadducts are para-compounds (∼59%), although meta-compounds (∼20%) and ortho-compounds (∼21%) are also present. Therefore, the thiol-ene reaction provides a robust approach for the convenient synthesis of mono-functional POSS derivatives and, potentially, of regio-selective multi-functionalized POSS derivatives as versatile nano-building blocks.
Co-reporter:Bo Ni, Xue-Hui Dong, Ziran Chen, Zhiwei Lin, Yiwen Li, Mingjun Huang, Qiang Fu, Stephen Z. D. Cheng and Wen-Bin Zhang
Polymer Chemistry 2014 vol. 5(Issue 11) pp:3588-3597
Publication Date(Web):11 Feb 2014
DOI:10.1039/C3PY01670F
Convenient synthesis of fluorinated molecular nanoparticles constitutes a major challenge in the preparation of fluoro shape amphiphiles. To facilitate a modular and efficient synthesis, a “clickable” fluorinated polyhedral oligomeric silsesquioxane functionalized with seven 1H,1H,2H,2H-heptadecafluorodecyl side chains and one alkyne group on its periphery (FPOSS-alkyne) was designed and synthesized. It was then used to prepare a series of FPOSS-containing polymers with various architectures via “click” chemistry. FPOSS was tethered onto either homo-polystyrene (PS) or polystyrene-block-poly(ethylene oxide) (PS-b-PEO) at precise locations, including the chain end (FPOSS-PS, FPOSS-PS-b-PEO) or junction point [PS-(FPOSS)-PEO], or distributed randomly along a PS chain (PS/FPOSS). This study demonstrates the chemical robustness of the novel building block and establishes a general and efficient approach to introduce fluorous molecular clusters onto polymers, especially for high molecular weight polymers or those polymers with high fluoro contents. These precisely defined FPOSS-containing polymers could serve as model compounds to study the self-assembly behaviors of these shape amphiphiles in the bulk, solution and thin film.
Co-reporter:Yiwen Li, Hao Su, Xueyan Feng, Zhao Wang, Kai Guo, Chrys Wesdemiotis, Qiang Fu, Stephen Z. D. Cheng and Wen-Bin Zhang
Polymer Chemistry 2014 vol. 5(Issue 21) pp:6151-6162
Publication Date(Web):21 Aug 2014
DOI:10.1039/C4PY01103A
One of the challenges in the precise synthesis of giant surfactants lies in the homogenous functionalization of a head with bulky ligands. In this article, we report the use of thiol-Michael “click” chemistry as a facile, modular and robust approach to address this issue. A giant surfactant with acryloxyl-functionalized POSS (ACPOSS) head was conveniently constructed from commercially available acrylo POSS and polystyrene (PS). Functional thiols with different sizes, such as 2-mercaptoethanol, 1H,1H,2H,2H-perfluoro-1-decanethiol, 1-thio-β-D-glucose tetraacetate (sugar-SH), and 2-naphthalenethiol, were attached onto the head of the ACPOSS-PS conjugate by thiol-Michael and thiol–ene reactions. It was found that while both the methods offer a straightforward and highly efficient approach to prepare uniform and precise giant surfactants with small thiol ligands, only the former proceeds without apparent side reactions when large and bulky thiols, such as sugar-SH and 2-naphthalenethiol, are used. The former method also eliminates the need for UV irradiation or heat initiation. Therefore, the mild condition, high efficiency, and broad functional group tolerance of thiol-Michael chemistry should further expand the scope of POSS-based giant surfactants with unparalleled possibilities for head surface chemistry manipulation, which provides numerous opportunities for nanofabrication by the direct self-assembly of giant surfactants.
Co-reporter:Xueyan Feng, Sunsheng Zhu, Kan Yue, Hao Su, Kai Guo, Chrys Wesdemiotis, Wen-Bin Zhang, Stephen Z. D. Cheng, and Yiwen Li
ACS Macro Letters 2014 Volume 3(Issue 9) pp:900
Publication Date(Web):August 29, 2014
DOI:10.1021/mz500422g
Head diversification of shape amphiphiles not only broadens the scope of supramolecular engineering for new self-organizing materials but also facilitates their potential applications in high technologies. In this letter, T10 azido-functionalized polyhedral oligomeric silsesquioxane (POSS) nanoparticle was used to construct new shape amphiphiles via sequential “click” chemistry for addressing two issues: (1) new symmetry of T10 POSS head could enrich the self-assembly behaviors of shape amphiphiles, and (2) copper-catalyzed azide–alkyne cycloaddition (CuAAC)-based head functionalization strategy allows the introduction of diverse functionalities onto POSS heads, including bulky ligands (i.e., isobutyl POSS) and UV-attenuating ones (i.e., ferrocene and 4-cyano-4′-biphenyl). This study expands the library of POSS-based shape amphiphiles with numerous possibilities for head manipulations, offering an important step toward new shape amphiphiles beyond traditional hydrophobic/hydrophilic nature for potential applications in giant molecule-based nanoscience and technology.
Co-reporter:Hao Su, Yiwen Li, Kan Yue, Zhao Wang, Pengtao Lu, Xueyan Feng, Xue-Hui Dong, Shuo Zhang, Stephen Z. D. Cheng and Wen-Bin Zhang
Polymer Chemistry 2014 vol. 5(Issue 11) pp:3697-3706
Publication Date(Web):24 Mar 2014
DOI:10.1039/C4PY00107A
Precise control of primary chemical structures, especially those of complex structures, is a prerequisite to understand the structure–property relationships of functional macromolecules. In this article, we report the rational design and tandem synthesis of three asymmetric giant gemini surfactants (AGGSs) of complex macromolecular structures based on polyhedral oligomeric silsesquioxane (POSS). In two cascading processes (typically within 5 hours), AGGSs can be synthesized where the length of the two polymer tails and the identity of the two POSS heads can be independently controlled and systematically varied. It represents a convenient, efficient, and modular way to prepare giant molecules with rigorous structural precision in only a few steps. This study expands the scope of synthetically available giant surfactants and facilitates further structural evolution toward even more complex macromolecules.
Co-reporter:Xue-Hui Dong, Xiaocun Lu, Bo Ni, Ziran Chen, Kan Yue, Yiwen Li, Lixia Rong, Tadanori Koga, Benjamin S. Hsiao, George R. Newkome, An-Chang Shi, Wen-Bin Zhang and Stephen Z. D. Cheng
Soft Matter 2014 vol. 10(Issue 18) pp:3200-3208
Publication Date(Web):27 Feb 2014
DOI:10.1039/C3SM52087K
A series of giant polymer–dendron conjugates with a dendron head and a linear polymer tail were synthesized via “click” chemistry between azide-functionalized polystyrene (PSN, N: degree-of-polymerization) and t-butyl protected, alkyne-functionalized second generation dendron (tD), followed by a deprotection process to generate a dendron termini possessing nine carboxylic acid groups. The molecular structures were confirmed by nuclear magnetic resonance, size-exclusion chromatographic analyses, and matrix-assisted laser desorption ionization time-of-flight mass spectra. These well-defined conjugates can serve as a model system to study the effects of the molecular geometries on the self-assembly behaviour, as compared with their linear analogues. Four phase morphologies found in flexible linear diblock copolymer systems, including lamellae, bicontinuous double gyroids, hexagonal packed cylinders, and body-centred cubic packed spheres, were observed in this series of conjugates based on the results of small angle X-ray scattering and transmission electron microscopy. All of the domain sizes in these phase separated structures were around or less than 10 nm. A ‘half’ phase diagram was constructed based on the experimental results. The geometrical effect was found not only to enhance the immiscibility between the PSN tail and dendron head, but also systematically shift all of the phase boundaries towards higher volume fractions of the PSN tails, resulting in an asymmetrical phase diagram. This study may provide a pathway to the construction of ordered patterns of sub-10 nm feature size using polymer–dendron conjugates.
Co-reporter:Tianzhi Yu, Yan Cao, Wenming Su, Chengcheng Zhang, Yuling Zhao, Duowang Fan, Mingjun Huang, Kan Yue and Stephen Z. D. Cheng
RSC Advances 2014 vol. 4(Issue 2) pp:554-562
Publication Date(Web):07 Nov 2013
DOI:10.1039/C3RA44432E
A new iridium complex containing coumarin derivative as a cyclometalated ligand (1L) and a carbazole-functionalized β-diketonate (2L) as the ancillary ligand, namely, Ir(III)bis(3-(pyridin-2-yl)coumarinato-N,C4)(1-(9-butyl-9H-carbazol-3-yl)-4,4,4-trifluoro-butane-1,3-dionato-O,O) (Ir(1L)2(2L)), was synthesized. The crystal structure of Ir(1L)2(2L) was determined via combined wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM), which showed π–π the interactions of Ir(1L)2(2L) molecules stacking along the crystal axes. The doped light-emitting diodes using this novel Ir(1L)2(2L) complex as the phosphorescent dopant were fabricated. At a Ir(1L)2(2L) concentration of 6.0 wt%, a green-yellow emitting OLED was achieved with a maximum external quantum efficiency (EQE) of 6.11% and a maximum luminous efficiency of 22.55 cd A−1 at the current density of 6.06 mA cm−2, and a maximum luminance of 6653 cd m−2 at 10.7 V. Furthermore, two reference complexes Ir(1L)2(acac) and Ir(1L)2(TTA) were also used as emitters to fabricate OLED devices with the same device configuration. The maximum luminous efficiency of Ir(1L)2(acac) doped device was measured to be 20.04 cd A−1 at 2.15 mA cm−2 (10.0 wt%), while the doped device of Ir(1L)2(TTA) had a maximum luminous efficiency of 16.59 cd A−1 at 1.36 mA cm−2. The better performances of Ir(1L)2(2L) doped devices could be largely attributed to an improved hole-transporting property due to the introduction of the carbazole moiety.
Co-reporter:Wen-Bin Zhang, Xinfei Yu, Chien-Lung Wang, Hao-Jan Sun, I-Fan Hsieh, Yiwen Li, Xue-Hui Dong, Kan Yue, Ryan Van Horn, and Stephen Z. D. Cheng
Macromolecules 2014 Volume 47(Issue 4) pp:1221-1239
Publication Date(Web):January 15, 2014
DOI:10.1021/ma401724p
In this Perspective, we present a unique approach to the design and synthesis of giant molecules based on “nanoatoms” for engineering structures across multiple length scales and controlling their macroscopic properties. Herein, “nanoatoms” refer to shape-persistent molecular nanoparticles (MNPs) with precisely defined chemical structures and surface functionalities that can serve as elemental building blocks for the precision synthesis of giant molecules by methods such as sequential “click” approach. Typical “nanoatoms” include those MNPs based on fullerenes, polyhedral oligomeric silsesquioxanes, polyoxometalates, and folded globular proteins. The resulting giant molecules are precisely defined macromolecules. They include, but are not limited to, giant surfactants, giant shape amphiphiles, and giant polyhedra. Giant surfactants are polymer tail-tethered “nanoatoms” where the two components have drastic chemical differences to impart amphiphilicity. Giant shape amphiphiles not only are built up by covalently bonded MNPs of distinct shapes where the self-assembly is driven by chemical interactions but also are largely influenced by the packing constraints of each individual shape. Giant polyhedra are either made of a large MNP or by deliberately placing “nanoatoms” at the vertices of a polyhedron. In general, giant molecules capture the essential structural features of their small-molecule counterparts in many ways but possess much larger sizes. They are recognized in certain cases as size-amplified versions of those counterparts, and often, they bridge the gap between small molecules and traditional macromolecules. Highly diverse, thermodynamically stable and metastable hierarchal structures are commonly observed in the bulk, thin film, and solution states of these giant molecules. Controlled structural variations by precision synthesis further reveal a remarkable sensitivity of their self-assembled structures to the primary chemical structures. Unconventional nanostructures can be obtained in confined environments or through directed self-assembly. All the results demonstrate that MNPs are unique elements for macromolecular science, providing a versatile platform for engineering nanostructures that are not only scientifically intriguing but also technologically relevant.
Co-reporter:Xinfei Yu;Yiwen Li;Xue-Hui Dong;Kan Yue;Zhiwei Lin;Xueyan Feng;Mingjun Huang;Wen-Bin Zhang
Journal of Polymer Science Part B: Polymer Physics 2014 Volume 52( Issue 20) pp:1309-1325
Publication Date(Web):
DOI:10.1002/polb.23571
ABSTRACT
Giant surfactants are polymer-tethered molecular nanoparticles (MNPs) and can be considered as a subclass of giant molecules. The MNPs serve as functionalized heads with persistent shape and volume, which may vary in size, symmetry, and surface chemistry. The covalent conjugation of MNPs and polymer tails affords giant surfactants with diverse composition and architecture. Synthetic strategies such as “grafting-from” and “grafting-onto” have been successfully applied to the precise synthesis of giant surfactants, which is further facilitated by the emergence of “click” chemistry reactions. In many aspects, giant surfactants capture the essential features of small-molecule surfactants, yet they have much larger sizes. They bridge the gap between small-molecule surfactants and traditional amphiphilic macromolecules. Their self-assembly behaviors in solution are summarized in this Review. Micelle formation is affected not only by their primary chemical structures, but also by the experimental conditions. This new class of materials is expected to deliver general implications on the design of novel functional materials based on MNP building blocks in the bottom-up fabrication of well-defined nanostructures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1309–1325
Co-reporter:Ming-Champ Lin, Chih-Hao Hsu, Hao-Jan Sun, Chien-Lung Wang, Wen-Bin Zhang, Yiwen Li, Hsin-Lung Chen, Stephen Z.D. Cheng
Polymer 2014 Volume 55(Issue 17) pp:4514-4520
Publication Date(Web):18 August 2014
DOI:10.1016/j.polymer.2014.07.008
Based on our recent understanding and development of functionalized molecular nanoparticles (MNPs) as building blocks for constructing various giant molecules, we report our efforts on design and synthesis of an asymmetric giant amphiphile, diBPOSS–C60, composed of one [60]fullerene (C60) covalently linked with two isobutyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS) MNPs. Its crystal structure and molecular packing were investigated. The compositional asymmetry between C60 and BPOSS led to a “sandwich-layered” molecular packing scheme, where a single layer of C60 is sandwiched between double BPOSS layers: a so-called “one-and-half-layered” structure. Within these layers, the molecules further organized into crystalline arrays. Interestingly, this compound can be viewed as size amplification of a class of atomically thin, two-dimensional layered transition metal dichalcogenides with the “one-and-half-layered” structure.
Co-reporter:Kan Wu, Mingjun Huang, Kan Yue, Chang Liu, Zhiwei Lin, Hao Liu, Wei Zhang, Chih-Hao Hsu, An-Chang Shi, Wen-Bin Zhang, and Stephen Z. D. Cheng
Macromolecules 2014 Volume 47(Issue 14) pp:4622-4633
Publication Date(Web):July 10, 2014
DOI:10.1021/ma501017e
A series of unique heterofunctionalized asymmetric giant “bolaform-like” surfactants composed of a polystyrene (PS) chain end-capped with two distinctly functionalized polyhedral oligomeric silsesquioxane (POSS) cages [one with seven isobutyl groups (BPOSS) and the other with 14 hydroxyl groups (DPOSS)] were designed and synthesized, and their self-assembly behaviors were investigated. Combining the atomic transfer radical polymerization using a BPOSS-containing initiator and the sequential “click” approach, BPOSS-PSn-DPOSS samples with different PS molecular weights were obtained. Investigation on their self-assembly behaviors revealed that they could form a variety of different ordered structures, such as lamellae, double gyroids, hexagonally packed cylinders, and body-center-cubic spheres, with feature sizes around or below 10 nm. Functional groups on the POSS cages govern the interaction parameters of different POSS cages with the PS interconnect and thus their compatibility. Hydrophilic DPOSS cages are phase-separated from the PS domains, while BPOSS cages are favorably associated within the PS domains. However, in the lamellae phase where the geometry of confinement seems compatible with the close-packing of BPOSS, the BPOSS cages tend to crystallize due to the existence of the flat interfaces, leading to further phase separation of the BPOSS cages from the PS interconnects. These results provide insights into the design of novel self-assembling materials based on POSS–polymer conjugates toward desired physical properties.
Co-reporter:Zhiwei Lin, Pengtao Lu, Xinfei Yu, Wen-Bin Zhang, Mingjun Huang, Kan Wu, Kai Guo, Chrys Wesdemiotis, Xiulin Zhu, Zhengbiao Zhang, Kan Yue, and Stephen Z. D. Cheng
Macromolecules 2014 Volume 47(Issue 13) pp:4160-4168
Publication Date(Web):June 23, 2014
DOI:10.1021/ma500696h
This paper reports the design and facile synthesis of a novel series of “nano-diamond-ring-like” giant surfactants composed of a functionalized hydrophilic polyhedral oligomeric silsesquioxane (such as dihydroxyl-functionalized DPOSS) or fullerene (such as carboxylic acid-functionalized AC60) head as the “diamond” and a hydrophobic, cyclic polystyrene (CPS) tail as the “ring”. The synthetic route combines several steps of “click-type” reactions, demonstrating highly efficient and modular features. Starting from a specifically designed initiator, trifunctional linear polystyrene (LPS) precursors bearing vinyl, bromo, and alkyne groups were prepared by atom transfer radical polymerization (ATRP). Upon the subsequent azidation of LPS, copper-catalyzed Huisgen [3 + 2] cycloaddition reaction was employed to afford vinyl-functionalized CPS ring in high yield and purity. The vinyl group was then subjected to the thiol–ene reaction to introduce an azide group onto the CPS, providing an azide-functionalized CPS (CPS-N3) as a “clickable” cyclic building block to construct giant molecules. Various “nano-diamond-ring-like” giant surfactants decorating with different “diamonds”, such as hydrophilic DPOSS or AC60 molecular nanoparticles, can be readily synthesized via the modular sequential “click” approaches based on this CPS-N3 building block. These giant surfactants with structural precision represent a novel member in the MNP-based giant surfactant family which might have distinct self-assembly behaviors compared to their linear analogues.
Co-reporter:Zhiwei Lin;Pengtao Lu;Chih-Hao Hsu;Dr. Kan Yue;Dr. Xue-Hui Dong;Hao Liu;Kai Guo; Chrys Wesdemiotis;Dr. Wen-Bin Zhang;Dr. Xinfei Yu; Stephen Z. D. Cheng
Chemistry - A European Journal 2014 Volume 20( Issue 37) pp:11630-11635
Publication Date(Web):
DOI:10.1002/chem.201402697
Abstract
Two molecular Janus particles based on amphiphilic [60]fullerene (C60) derivatives were designed and synthesized by using the regioselective Bingel–Hirsh reaction and the click reaction. These particles contain carboxylic acid functional groups, a hydrophilic fullerene (AC60), and a hydrophobic C60 in different ratios and have distinct molecular architectures: 1:1 (AC60–C60) and 1:2 (AC60–2C60). These molecular Janus particles can self-assemble in solution to form aggregates with various types of micellar morphology. Whereas vesicular morphology was observed for both AC60–C60 and AC60–2C60 in tetrahydrofuran, in a mixture of N,N-dimethylformamide (DMF)/water, spherical micelles and cylindrical micelles were observed for AC60–C60 and AC60–2C60, respectively. A mechanism of formation was tentatively proposed based on the effects of molecular architecture and solvent polarity on self-assembly.
Co-reporter:Zhao Wang, Yiwen Li, Xue-Hui Dong, Xinfei Yu, Kai Guo, Hao Su, Kan Yue, Chys Wesdemiotis, Stephen Z. D. Cheng and Wen-Bin Zhang
Chemical Science 2013 vol. 4(Issue 3) pp:1345-1352
Publication Date(Web):25 Jan 2013
DOI:10.1039/C3SC22297G
This paper reports our recent investigations in the synthesis, characterization, and solution self-assembly of giant gemini surfactants consisting of two hydrophilic carboxylic acid-functionalized polyhedral oligomeric silsesquioxane (APOSS) heads and two hydrophobic polystyrene (PS) tails covalently linked via a rigid spacer (p-phenylene or biphenylene) (PS–(APOSS)2–PS). The sequential “click” approach was employed in the synthesis, which involved thiol–ene mono-functionalization of vinyl-functionalized POSS, Cu(I)-catalyzed Huisgen [3 + 2] azide–alkyne cycloadditions for “grafting” polymer tails onto the POSS cages, and subsequent thiol–ene “click” surface functionalization. The study of their self-assembly in solution revealed a morphological transition from vesicles to wormlike cylinders and further to spheres as the degree of ionization of the carboxylic acid groups on POSS heads increases. It was found that the PS tails are generally less stretched in the micellar cores of these giant gemini surfactants than those of the corresponding single-tailed (APOSS–PS) giant surfactant. It was further observed that the PS tail conformations in the micelles were also affected by the length of the rigid spacers where the one with longer spacer exhibits even more stretched PS tail conformation. Both findings could be explained by the topological constraint imposed by the short rigid spacer in PS–(APOSS)2–PS gemini surfactants. This constraint effectively increases the local charge density and leads to an anisotropic head shape that requires a proper re-distribution of the APOSS heads on the micellar surface to minimize the total electrostatic repulsive free energy. The study expands the scope of giant molecular shape amphiphiles and has general implications in the basic physical principles underlying their solution self-assembly behaviors.
Co-reporter:Yiwen Li, Zhao Wang, Jukuan Zheng, Hao Su, Fei Lin, Kai Guo, Xueyan Feng, Chrys Wesdemiotis, Matthew L. Becker, Stephen Z. D. Cheng, and Wen-Bin Zhang
ACS Macro Letters 2013 Volume 2(Issue 11) pp:1026
Publication Date(Web):November 5, 2013
DOI:10.1021/mz400519c
Rapid and precise synthesis of macromolecules has been a grand challenge in polymer chemistry. In this letter, we describe a convenient, rapid, and robust strategy for a one-pot synthesis of various precisely defined giant surfactants based on polyhedral oligomeric silsesquioxane (POSS). The method combines orthogonal oxime ligation, strain-promoted azide–alkyne cycloaddition (SPAAC), and thiol–ene “click” coupling. The process is usually completed within 0.5–2 h and does not require chromatography methods for purification. With near quantitative conversion efficiency, the method yields giant surfactants with distinct topologies, including single-tailed and asymmetric, multitailed giant surfactants. Both polymer tail composition and POSS surface chemistry are controlled precisely and tuned independently, enabling the design and preparation of new classes of giant surfactants.
Co-reporter:Hao Su, Jukuan Zheng, Zhao Wang, Fei Lin, Xueyan Feng, Xue-Hui Dong, Matthew L. Becker, Stephen Z. D. Cheng, Wen-Bin Zhang, and Yiwen Li
ACS Macro Letters 2013 Volume 2(Issue 8) pp:645
Publication Date(Web):July 15, 2013
DOI:10.1021/mz4002723
This letter reports a sequential triple “click” chemistry method for the precise synthesis of functional polyhedral oligomeric silsesquioxane (POSS)-based multiheaded and multitailed giant surfactants. A vinyl POSS-based heterobifunctional building block possessing two alkyne groups of distinct reactivity was used as a robust and powerful “clickable” precursor for ready access to a variety of POSS-based shape amphiphiles with complex architectures. The synthetic approach involves sequentially performed strain-promoted azide–alkyne cycloaddition (SPAAC), copper-catalyzed azide–alkyne cycloaddition (CuAAC), and thiol–ene “click” coupling (TECC). Specifically, the first SPAAC reaction was found to be highly selective with no complications from the vinyl groups and terminal alkynes in the precursor. The method expands the toolbox of sequential “click” approaches and broadens the scope of synthetically available giant surfactants for further study on structure–property relationships.
Co-reporter:Kan Yue, Chang Liu, Kai Guo, Kan Wu, Xue-Hui Dong, Hao Liu, Mingjun Huang, Chrys Wesdemiotis, Stephen Z. D. Cheng and Wen-Bin Zhang
Polymer Chemistry 2013 vol. 4(Issue 4) pp:1056-1067
Publication Date(Web):02 Nov 2012
DOI:10.1039/C2PY20881D
This paper reports the molecular design and click syntheses of novel shape amphiphiles with molecular architectures beyond conventional giant surfactants. They include (1) the giant bolaform surfactant which consists of a polystyrene (PS) chain tethered with one hydrophilic POSS cage at each end of the chain (DPOSS–PS–DPOSS); (2) the giant gemini surfactant which contains two hydrophilic POSS cages and two PS tails tethered at one junction point (2DPOSS–2PS); and (3) the multi-headed giant surfactant which is composed of three hydrophilic POSS cages tethered at one end of a PS chain (3DPOSS–PS). The syntheses were achieved in a modular and efficient fashion following the sequential click approach in good yields, providing easy access to a family of shape amphiphiles with precise chemical structures and fine-tuned interactions for a systematic study of structure–property relationships.
Co-reporter:Kan Yue;Jinlin He;Chang Liu;Mingjun Huang
Chinese Journal of Polymer Science 2013 Volume 31( Issue 1) pp:71-82
Publication Date(Web):2013 January
DOI:10.1007/s10118-013-1215-x
“Click chemistry” is, by definition, a general functionalization methodology (GFM) and its marriage with living anionic polymerization is particularly powerful in precise macromolecular synthesis. This paper reports the synthesis of a “clickable” middle-chain azide-functionalized polystyrene (mPS-N3) by anionic polymerization and its application in the preparation of novel shape amphiphiles based on polyhedral oligomeric silsesquioxane (POSS). The mPS-N3 was synthesized by coupling living poly(styryl)lithium chains (PSLi) with 3-chloropropylmethyldichlorosilane and subsequent nucleophilic substitution of the chloro group in the presence of sodium azide. Excess PSLi was end-capped with ethylene oxide to facilitate its removal by flash chromatography. The mPS-N3 was then derived into a giant lipid-like shape amphiphile in two steps following a sequential “click” strategy. The copper(I)-catalyzed azide-alkyne cycloaddition between mPS-N3 and alkyne-functionalized vinyl-substituted POSS derivative (VPOSS-alkyne) ensured quantitative ligation to give polystyrene with VPOSS tethered at the middle of the chain (mPS-VPOSS). The thiol-ene reaction with 1-thioglycerol transforms the vinyl groups on the POSS periphery to hydroxyls, resulting in an amphiphilic shape amphiphile, mPS-DPOSS. This synthetic approach is highly efficient and modular. It demonstrates the “click” philosophy of facile complex molecule construction from a library of simple building blocks and also suggests that mPS-N3 can be used as a versatile “clickable” motif in polymer science for the precise synthesis of complex macromolecules.
Co-reporter:Xinfei Yu;Kan Yue;I-Fan Hsieh;Yiwen Li;Xue-Hui Dong;Chang Liu;Yu Xin;Hsiao-Fang Wang;An-Chang Shi;George R. Newkome;Rong-Ming Ho;Er-Qiang Chen;Wen-Bin Zhang
PNAS 2013 110 (25 ) pp:10078-10083
Publication Date(Web):2013-06-18
DOI:10.1073/pnas.1302606110
The engineering of structures across different length scales is central to the design of novel materials with controlled macroscopic
properties. Herein, we introduce a unique class of self-assembling materials, which are built upon shape- and volume-persistent
molecular nanoparticles and other structural motifs, such as polymers, and can be viewed as a size-amplified version of the
corresponding small-molecule counterparts. Among them, “giant surfactants” with precise molecular structures have been synthesized
by “clicking” compact and polar molecular nanoparticles to flexible polymer tails of various composition and architecture
at specific sites. Capturing the structural features of small-molecule surfactants but possessing much larger sizes, giant
surfactants bridge the gap between small-molecule surfactants and block copolymers and demonstrate a duality of both materials
in terms of their self-assembly behaviors. The controlled structural variations of these giant surfactants through precision
synthesis further reveal that their self-assemblies are remarkably sensitive to primary chemical structures, leading to highly
diverse, thermodynamically stable nanostructures with feature sizes around 10 nm or smaller in the bulk, thin-film, and solution
states, as dictated by the collective physical interactions and geometric constraints. The results suggest that this class
of materials provides a versatile platform for engineering nanostructures with sub-10-nm feature sizes. These findings are
not only scientifically intriguing in understanding the chemical and physical principles of the self-assembly, but also technologically
relevant, such as in nanopatterning technology and microelectronics.
Co-reporter:Fu-Ai Teng;Dr. Yan Cao;Yuan-Jiang Qi;Mingjun Huang; Zhe-Wen Han; Stephen Z. D. Cheng;Dr. Wen-Bin Zhang; Hui Li
Chemistry – An Asian Journal 2013 Volume 8( Issue 6) pp:1223-1231
Publication Date(Web):
DOI:10.1002/asia.201300043
Abstract
A series of sphere–rod shape amphiphiles, in which a [60]fullerene (C60) sphere was connected to the center of an oligofluorene (OF) rod through a rigid linkage (OF-C60), were designed and synthesized. Alkyl chains of various lengths were attached onto the OFs on both sides of the C60 spheres. These compounds, denoted as alkyl-OF-C60, were fully characterized by 1H NMR, 13C NMR, and FTIR spectroscopy and by MALDI-TOF mass spectrometry. The morphologies and structures of their crystals were elucidated by wide-angle X-ray diffraction (WAXD) and by electron diffraction in transmission electron microscopy (TEM). Butyl-OF-C60 forms a monoclinic unit cell (a=1.86, b=3.96, c=2.24 nm; α=γ=90°, β=68°; space group P2), octyl-OF-C60 also forms a monoclinic unit cell (a=2.21, b=4.06, c=1.81 nm; α=γ=90°, β=75.5°; space group C2m), and dodecanyl-OF-C60 forms a triclinic structure (a=1.82, b=4.35, c=2.26 nm; α=93.1°, β=94.5°, γ=92.7°; space group P1). The inequivalent spheres and rods were found to pack into an alternating layered structure of C60 and OF in the crystals, thus resembling a “double-cable” structure. UV/Vis absorption spectroscopy revealed an electron perturbation between the two individual chromophores (C60 and OF) in their ground states. Fluorescence spectroscopy exhibited complete fluorescence quenching of their solutions in toluene, thus suggesting an effective energy transfer from OF to C60. Cyclic voltammetry indicated that the energy-level profiles of C60 and OF remained essentially unchanged. This work has broad implications in terms of understanding the self-assembly and molecular packing of conjugated materials in crystals and has potential applications in organic field-effect transistors and bulk heterojunction solar cells.
Co-reporter:Xue-Hui Dong, Ryan Van Horn, Ziran Chen, Bo Ni, Xinfei Yu, Andreas Wurm, Christoph Schick, Bernard Lotz, Wen-Bin Zhang, and Stephen Z. D. Cheng
The Journal of Physical Chemistry Letters 2013 Volume 4(Issue 14) pp:2356-2360
Publication Date(Web):July 1, 2013
DOI:10.1021/jz401132j
We describe highly unconventional situations in which the polymer chain ends remain trapped in and are located in the middle of the lamellar crystal core as defects. Such structures are observed in giant molecular shape amphiphiles constructed by a polyhedral silsesquioxane (POSS) nanoparticle tethered with a poly(ethylene oxide) (PEO) tail. The cross-sectional area of the POSS located on the PEO lamellar surfaces imposes that the crystalline, chain-folded PEO tails generate a surface area that is at least comparable to the POSS requirements. Metastable PEO crystal structures with 1.5, 2, and 2.5 stem numbers have been observed with different thermodynamic stabilities.Keywords: chain folding; crystallization; molecular nanoparticles; poly(ethylene oxide);
Co-reporter:Xinfei Yu ; Wen-Bin Zhang ; Kan Yue ; Xiaopeng Li ; Hao Liu ; Yu Xin ; Chien-Lung Wang ; Chrys Wesdemiotis
Journal of the American Chemical Society 2012 Volume 134(Issue 18) pp:7780-7787
Publication Date(Web):April 26, 2012
DOI:10.1021/ja3000529
This paper reports a comprehensive study on the synthesis and self-assembly of two model series of molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC60) tethered with one or two polystyrene (PS) chain(s) at one junction point (PSn–AC60 and 2PSn–AC60). The synthesis highlighted the regiospecific multiaddition reaction for C60 surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C60 and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as molecular topology, polymer tail length, and initial molecular concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low molecular concentration range of equal or less than 0.25 (wt) %, micellar morphology of the series of PSn–AC60 studied was always spheres, while the series of 2PSn–AC60 formed vesicles. Particularly, PS44–AC60 and 2PS23–AC60 are synthesized as a topological isomer pair of these shape amphiphiles. PS44–AC60 formed spherical micelles while 2PS23–AC60 generated bilayer vesicles under identical conditions. The difference in the self-assembly of PSn–AC60 and 2PSn–AC60 was understood by the molecular shape aspect ratio. The stretching ratio of PS tails decreased with increasing PS tail length in the spherical micelles of PSn–AC60, indicating a micellar behavior that changes from small molecular surfactant-like to amphiphilic block copolymer-like. For the series of PSn–AC60 in the high molecular concentration range [>0.25 (wt) %], their micellar morphological formation of spheres, cylinders, and vesicles was critically dependent upon both the initial molecular concentration and the PS tail length. On the other hand, the series of 2PSn–AC60 remained in the state of bilayer vesicles in the same concentration range. Combining both of the experimental results obtained in the low and high molecular concentrations, a systematic morphological phase diagram was constructed for the series of PSn–AC60 with different PS tail lengths. The versatile and concentration-sensitive phase behaviors of these molecular shape amphiphiles are unique and have not been systematically explored in the traditional surfactants and block copolymers systems.
Co-reporter:Jinlin He, Kan Yue, Yuqing Liu, Xinfei Yu, Peihong Ni, Kevin A. Cavicchi, Roderic P. Quirk, Er-Qiang Chen, Stephen Z. D. Cheng and Wen-Bin Zhang
Polymer Chemistry 2012 vol. 3(Issue 8) pp:2112-2120
Publication Date(Web):17 May 2012
DOI:10.1039/C2PY20101A
This paper reports the design and synthesis of fluoroalkyl-functionalized polyhedral oligomeric silsesquioxane (FPOSS)-based shape amphiphiles with two distinct topologies: (i) mono-tethered FPOSS-poly(ε-caprolactone) (PCL) and (ii) FPOSS tethered with two polymer chains possessing different compositions, namely, polystyrene (PS) and PCL, denoted as PS–(FPOSS)–PCL. The synthetic strategy features an efficient “growing-from” and “click-functionalization” approach. From a monohydroxyl-functionalized heptavinyl POSS, a PCL chain was grown via ring opening polymerization (ROP) of ε-caprolactone; subsequent thiol–ene “click” chemistry with 1H,1H,2H,2H-perfluoro-1-decanethiol allowed the facile introduction of seven perfluorinated alkyl chains onto the POSS head. Similarly, PS–(FPOSS)–PCL was synthesized from a PS precursor bearing both hydroxyl group and heptavinyl POSS at the ω-end, which was prepared by living anionic polymerization and hydrosilylation. The compounds were fully characterized by 1H NMR, 13C NMR, FT-IR spectroscopy, MALDI-TOF mass spectrometry, and size exclusion chromatography. The introduction of perfluorinated molecular cluster into polymers is expected to make them surface-active while the interplay between crystallization and fluorophobic/fluorophilic bulk phase separation in these shape amphiphiles shall lead to intriguing self-assembly behavior and novel hierarchical structures. This study has demonstrated FPOSS as a versatile building block in the construction of shape amphiphiles and established a general and efficient method to introduce such fluorous molecular clusters into polymers.
Co-reporter:Xue-Hui Dong, Wen-Bin Zhang, Yiwen Li, Mingjun Huang, Shuo Zhang, Roderic P. Quirk and Stephen Z. D. Cheng
Polymer Chemistry 2012 vol. 3(Issue 1) pp:124-134
Publication Date(Web):08 Nov 2011
DOI:10.1039/C1PY00435B
A series of [60]fullerene (C60)-containing poly(ethylene oxide)-block-polystyrene (PEO-b-PS) with various numbers and different locations of C60 along the polymer chains were designed and synthesized via a combination of “click” chemistry and living/controlled polymerization techniques such as anionic polymerization, atom transfer radical polymerization, and reversible addition–fragmentation chain transfer polymerization. One C60 was tethered either to the end of a PS block (PEO-b-PS-C60) or at the junction point between PS and PEO blocks [PEO-(C60)-PS]; while multiple C60s could be attached randomly along the PS block (PEO-b-PS/C60). The reaction conditions were carefully controlled to ensure a quantitative C60 functionality at precise locations in the case of PEO-b-PS-C60 and PEO-(C60)-PS and to avoid crosslinking in the synthesis of PEO-b-PS/C60. The results have implications in the precision synthesis of fullerene polymers in general. These C60-containing diblock copolymers possess different composition, diverse architecture, and high fullerene functionality. They can serve as model “shape amphiphiles” for the construction of complex hierarchical structures via the interplay between C60–C60 aggregation and block copolymer self-assembly/micro-phase separation.
Co-reporter:Guoliang Zhang, Xuemei Zhai, Zhenpeng Ma, Liuxin Jin, Ping Zheng, Wei Wang, Stephen Z. D. Cheng, and Bernard Lotz
ACS Macro Letters 2012 Volume 1(Issue 1) pp:217
Publication Date(Web):December 22, 2011
DOI:10.1021/mz2001109
A series of single-layer crystal patterns were observed in ultrathin films of 10 poly(ethylene oxide) fractions of molecular weights ranging from 2.02k to 932.0k g/mol. Morphology transitions between these different crystal patterns were quantitatively identified, and a morphology diagram with respect to supercooling and molecular weight dependencies was constructed. This will foster understanding of the macromolecular effects on the crystal pattern formation and selection critically associated with the parameters of molecular diffusion length and growth anisotropy.
Co-reporter:Yiwen Li, Xue-Hui Dong, Kai Guo, Zhao Wang, Ziran Chen, Chrys Wesdemiotis, Roderic P. Quirk, Wen-Bin Zhang, and Stephen Z. D. Cheng
ACS Macro Letters 2012 Volume 1(Issue 7) pp:834
Publication Date(Web):June 19, 2012
DOI:10.1021/mz300196x
A series of shape amphiphiles based on functionalized polyhedral oligomeric silsesquioxane (POSS) head tethered with two polymeric tails of symmetric or asymmetric compositions was designed and synthesized using sequential “grafting-from” and “click” surface functionalization. The monofunctionalization of octavinylPOSS was performed using thiol–ene chemistry to afford a dihydroxyl-functionalized POSS that was further derived into precisely defined homo- and heterobifunctional macroinitiators. Polymer tails, such as polycaprolactone and polystyrene, could then be grown from these POSS-based macroinitiators with controlled molecular weight via ring-opening polymerization and atom transfer radical polymerization (ATRP). The vinyl groups on POSS were found to be compatible with ATRP conditions. These macromolecular precursors were further modified by thiol–ene chemistry to install surface functionalities onto the POSS cage. The polymer chain composition and POSS surface chemistry can thus be tuned separately in a modular and efficient way.
Co-reporter:I-Fan Hsieh, Hao-Jan Sun, Qiang Fu, Bernard Lotz, Kevin A. Cavicchi and Stephen Z. D. Cheng
Soft Matter 2012 vol. 8(Issue 30) pp:7937-7944
Publication Date(Web):02 Jul 2012
DOI:10.1039/C2SM25749A
The solvent-induced spherical structure in a polystyrene-block-polydimethylsiloxane (PS-b-PDMS) block copolymer was obtained and stabilized by preparing both the bulk and thin films from propylene glycol methyl ether acetate (PGMEA) solutions. The diblock copolymer possessed a total molecular weight of 42 kDa with a PS volume fraction of 72.2%, and it formed a cylindrical phase structure in the equilibrium bulk state. During thermal annealing, only changes in the sphere size and packing rearrangement were found. In contrast, a unique structure evolution route was observed during solvent treatments. Under a controlled vapour of a PS selective solvent, an oscillation of the structural transition between spheres and cylinders was observed in the thin films. The kinetics of this oscillation of structural transition was found to be closely related to the solvent vapour concentration and film thickness. This experiment revealed a unique ordering pathway towards the equilibrium structure in the thin film for this strongly segregated PS-b-PDMS diblock copolymer.
Co-reporter:Hao-Jan Sun, Chien-Lung Wang, I-Fan Hsieh, Chih-Hao Hsu, Ryan M. Van Horn, Chi-Chun Tsai, Kwang-Un Jeong, Bernard Lotz and Stephen Z. D. Cheng
Soft Matter 2012 vol. 8(Issue 17) pp:4767-4779
Publication Date(Web):13 Mar 2012
DOI:10.1039/C2SM07332C
A precisely defined molecular Janus compound based on asymmetric tapered 1,4-bis[3,4,5-tris(alkan-1-yloxy)benzamido] benzene bisamide (abbreviated as C22PhBAEO3) was designed and synthesized, and its phase behavior was fully investigated. The C22PhBAEO3 compound possesses a rigid core with three aromatic rings connected with amide bonds which possess the ability to form hydrogen (H) bonds. Three hydrophobic alkyl flexible tails and three hydrophilic flexible methyl terminated triethylene glycol tails are located at the other end. Major phase transitions and their origins in C22PhBAEO3 were studied via DSC and 1D WAXD techniques. Its hierarchical supramolecular crystal structure was further identified through combined techniques of 2D WAXD and SAXS as well as SAED. Results based on computer simulations confirmed the structure determination. It was found that the C22PhBAEO3 possesses three phases through various thermal treatments including a micro-phase separated columnar liquid crystal (col.) phase, a metastable crystal I phase and a stable crystal II phase. Among them, the crystal II phase showed that the columnar structure possesses 3D inter-column order and highly crystalline alkyl tails with a long-range overall orientational order. Four C22PhBAEO3 molecules self-assembled into a phase-separated disc with an ellipsoidal shape having a C2 symmetry along the disc normal. These discs then stacked on top of each other to generate a 1D asymmetric column through H-bonding, and further packed into a 3D long-range ordered monoclinic lattice. The unit cell parameters of this lattice were determined to be a = 5.08 nm, b = 2.41 nm, c = 0.98 nm, α = 90°, β = 90°, and γ = 70.5°. The alkyl chain tails crystallize within the hydrophobic layers and possess a relatively fixed orientation with respect to the column packing due to the selective interactions based on the hydrophobic/hydrophilic microphase separation. Both phase behaviour and unit cell structure showed significant difference compared with the symmetrically tapered counterparts. The results provided a new approach of fine-tuning not only in the Janus supramolecular structures but also in the formation pathway of the self-assembling process in order to meet the specific requirements for optical and biological applications.
Co-reporter:Wen-Bin Zhang;YingFeng Tu;Hao-Jan Sun;Kan Yue;Xiong Gong
Science China Chemistry 2012 Volume 55( Issue 5) pp:749-754
Publication Date(Web):2012 May
DOI:10.1007/s11426-011-4422-8
A polyhedral oligomeric silsesquioxane-[60]fullerene (POSS-C60) dyad was designed and used as a novel electron acceptor for bulk heterojunction (BHJ) polymer solar cells (PSCs) with an inverted device configuration. The studies of time-resolved photoinduced absorption of the pristine thin film of poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(4,7-bis (2-thienyl)-2,1,3-benzothiadiazole)-5,5′-diyl] (SiPCPDTBT) and the composite thin film of SiPCPDTBT:POSS-C60 indicated efficient electron transfer from SiPCPDTBT to POSS-C60 with inhibited back-transfer. BHJ PSCs made by SiPCPDTBT mixed with POSS-C60 yielded the power conversion efficiencies (PCEs) of 1.50%. Under the same operational conditions, PCEs observed from BHJ PSCs made by SiPCPDTBT mixed with [6,6]-phenyl-C61-butyric acid methyl ester were 0.92%. These results demonstrated that POSS-C60 is a potentially good electron acceptor for inverted BHJ PSCs.
Co-reporter:Lian Wang, Xinfei Yu, Shuguang Yang, Joseph X. Zheng, Ryan M. Van Horn, Wen-Bin Zhang, Junting Xu, and Stephen Z. D. Cheng
Macromolecules 2012 Volume 45(Issue 8) pp:3634-3638
Publication Date(Web):April 9, 2012
DOI:10.1021/ma3002752
Co-reporter:Kan Yue, Chang Liu, Kai Guo, Xinfei Yu, Mingjun Huang, Yiwen Li, Chrys Wesdemiotis, Stephen Z. D. Cheng, and Wen-Bin Zhang
Macromolecules 2012 Volume 45(Issue 20) pp:8126-8134
Publication Date(Web):October 1, 2012
DOI:10.1021/ma3013256
This paper reports a highly efficient and modular sequential “click” approach for the syntheses of shape amphiphiles based on polymer-tethered polyhedral oligomeric silsesquioxane (POSS). This approach combines both “grafting-to” and “post-functionalization” strategies. It involves the copper-catalyzed Huisgen [3 + 2] cycloaddition (CuAAC) for POSS–polymer ligation and subsequent thiol–ene addition reaction for POSS cage functionalization. Starting from a readily available POSS precursor bearing one alkyne and seven vinyl groups (VPOSS–alkyne), the CuAAC reaction is effective in ensuring the stoichiometric bonding between POSS and azide-functionalized polymers, with no need for fractionation in the purification process. The modularity was demonstrated in two representative polymer systems, hydrophobic polystyrene (PS) and hydrophilic poly(ethylene oxide) (PEO), by the synthesis of VPOSS–PS and VPOSS–PEO. The thiol–ene reaction was subsequently applied to convert all the vinyl groups on the POSS cage quantitatively into various functional groups, including carboxylic acids, hydroxyls, and alkyls, thereby introducing amphiphilicity to drive self-assembly. Such shape amphiphiles are novel model systems for the study of their self-assembly behaviors, hierarchal structure formation, and functional properties in both the solution and bulk states. Aiming to fulfill the “click” philosophy, the sequential “click” approach described here is robust and efficient for rapid construction of functional shape amphiphiles with complex structures and diverse molecular architectures.
Co-reporter:Wen-Bin Zhang, Jinlin He, Kan Yue, Chang Liu, Peihong Ni, Roderic P. Quirk, and Stephen Z. D. Cheng
Macromolecules 2012 Volume 45(Issue 21) pp:8571-8579
Publication Date(Web):2017-2-22
DOI:10.1021/ma301597f
A new approach has been developed for the preparation of well-defined, eight-arm star polymers via the addition of poly(styryl)lithium to octavinylPOSS in benzene. The reaction proceeds rapidly to completion (within 5 min for molecular weight of each arm up to 33 kg/mol), forming predominantly eight-arm star polymers. The products were purified by fractionation and fully characterized by 1H NMR, 13C NMR, 29Si NMR, FT-IR, MALDI-TOF mass spectrometry, and size exclusion chromatography. Compared to conventional coupling approaches, this process is found to be less sensitive to the stoichiometry of the reactants and the molecular weight of each arm. A mechanism based on cross-association and intra-aggregate addition is invoked to account for this unusual observation. As evidence, when a polar solvent, tetrahydrofuran, or a strongly coordinating and disassociating Lewis base, tetramethylethylenediamine, was used to dissociate the living polymer chains, star polymers with lower average arm numbers than those of the products synthesized in pure benzene were formed at the same stoichiometry of the reactants. The method has general implications in the understanding of the reactive nature of the living anionic polymerization and may find practical application in the synthesis of functional star polymers of diverse compositions and architectures.
Co-reporter:Yiwen Li ; Wen-Bin Zhang ; I-Fan Hsieh ; Guoliang Zhang ; Yan Cao ; Xiaopeng Li ; Chrys Wesdemiotis ; Bernard Lotz ; Huiming Xiong
Journal of the American Chemical Society 2011 Volume 133(Issue 28) pp:10712-10715
Publication Date(Web):June 16, 2011
DOI:10.1021/ja202906m
The design, synthesis, and self-assembly of a series of precisely defined, nonspherical, polyhedral oligomeric silsesquioxane (POSS)-based molecular Janus particles are reported. The synthesis aims to fulfill the “click” philosophy by using thiol–ene chemistry to efficiently install versatile functionalities on one of the POSS cages. In such a way, both the geometrical and chemical symmetries were broken to create the Janus feature. These particles self-organize into hierarchically ordered supramolecular structures in the bulk. For example, the Janus particle with isobutyl groups on one POSS and carboxylic groups on the other self-assembles into a bilayered structure with head-to-head, tail-to-tail arrangements of each particle, which further organize into a three-dimensional orthorhombic lattice. While the ordered structure in the layers was lost upon heating via a first-order transition, the bilayered structure persisted throughout. This study provides a model system of well-defined molecular Janus particles for the general understanding of their self-assembly and hierarchical structure formation in the condensed state.
Co-reporter:Hao-Jan Sun, Yingfeng Tu, Chien-Lung Wang, Ryan M. Van Horn, Chi-Chun Tsai, Matthew J. Graham, Bin Sun, Bernard Lotz, Wen-Bin Zhang and Stephen Z. D. Cheng
Journal of Materials Chemistry A 2011 vol. 21(Issue 37) pp:14240-14247
Publication Date(Web):14 May 2011
DOI:10.1039/C1JM10954E
A shape amphiphile composed of covalently linked spherical and cubic nanoparticles with distinct symmetry ([60]fullerene (C60) and polyhedral oligomeric silsesquioxane (POSS)) was synthesized and its solid state structures were characterized. The two types of nanoparticles are known to be generally immiscible, but they were connected with a short covalent linkage forming an organic–inorganic dyad (POSS–C60) which exhibited interesting crystallization characteristics. Crystals of the dyad exhibited polymorphism with two different crystal structures: an orthorhombic and a hexagonal unit cell with symmetry groups of P21212 and P6, respectively, both of which formed an alternating bi-layered structure of POSS and C60. The different symmetry groups in the polymorphs were attributed to the different packing orientations of the POSS within each layer. In the orthorhombic unit cell, one set of the edges of the POSS moieties is parallel to the c-axis; while in the hexagonal unit cells the body-diagonal is parallel to the c-axis of the crystal. Based on the crystal packing structure and density differential, it has been determined that the hexagonal unit cell structure is the more thermodynamically stable phase. This type of bi-layered structure with an alternating conductive fullerene and insulating POSS layer structure is of great interest for various potential applications such as nano-capacitors.
Co-reporter:Chien-Lung Wang, Wen-Bin Zhang, Chih-Hao Hsu, Hao-Jan Sun, Ryan M. Van Horn, Yingfeng Tu, Denis V. Anokhin, Dimitri A. Ivanov and Stephen Z. D. Cheng
Soft Matter 2011 vol. 7(Issue 13) pp:6135-6143
Publication Date(Web):25 May 2011
DOI:10.1039/C1SM05381G
When a molecule is constructed from geometrically isotropic [such as [60]fullerene (C60)] and anisotropic (such as porphyrin) units, as in the case of a trans-di-C60-substituted Zn porphyrin derivative (diZnCPD), great interest lies in the understanding of their individual contributions to structural formations and phase transitions. For this purpose, the compound, diZnCPD, was designed and synthesized. Its phase behavior was investigated viadifferential scanning calorimetry (DSC) and polarized light optical microscopy (POM) and its supramolecular structure was elucidated viawide-angle X-ray diffraction (WAXD) and selective area electron diffraction (SAED) in transmission electron microscopy (TEM). The diZnCPD possesses a polymorphism in its ordered structures. When cooled from the isotropic (I) phase with experimentally accessible rates, instead of transferring into its ultimate stable phase, this compound formed a less ordered, metastable phase with a layered structure at 152 °C. Annealing this metastable phase enabled a further transformation into a stable phase with a higher transition temperature. As such, this metastable phase is monotropic. The formation of the stable phase was thus thermodynamically favorable, but kinetically more difficult (with a higher barrier for the transformation). Direct formation of this stable phase from the I state was unsuccessful even after prolonged isothermal experiments over several days above 152 °C, indicating that the formation barrier of this stable phase is extremely high. The thermally stable phase possessed a supramolecular structure with a triclinic unit cell of a = 3.34 nm, b = 2.01 nm, c = 1.88 nm, α = 89°, β = 98°, and γ = 90°. Detailed structural analysis revealed that this is a donor–acceptor separated structure of C60s and porphyrins nearly along the [01] direction within which the zig-zag shaped C60 channels are along the [001] direction of the unit cell. We believe this is the first example of generating a donor–acceptor separated structure of C60s and porphyrins in the bulk through a thermal annealing process. This structure provides promising potential for the use of this material to fabricate supramolecular electronic devices without utilizing a solvent process.
Co-reporter:Wen-Bin Zhang, Jinlin He, Xuehui Dong, Chien-Lung Wang, Hui Li, Fuai Teng, Xiaopeng Li, Chrys Wesdemiotis, Roderic P. Quirk, Stephen Z.D. Cheng
Polymer 2011 Volume 52(Issue 19) pp:4221-4226
Publication Date(Web):1 September 2011
DOI:10.1016/j.polymer.2011.07.026
For the first time, the scope of Fisher esterification has been extended to fullerene derivatives to improve the synthesis of alkyne-functionalized fullerenes (fullerynes) using 1-chloronaphthalene as a solvent and a specially-designed, home-made reactor to promote high yield. The design allows for higher solubility of fullerene derivatives and a continuous azeotropic distillation for the removal of water to drive the reaction to completion with yields >90%. Both fullerynes (Fulleryne01 and Fulleryne02) were found to “click” to polymers, such as azide-functionalized poly(ɛ-caprolactone) (PCL-N3), in high efficiency without the need for fractionation. As evidenced by 1H NMR, 13C NMR, size exclusion chromatography, and matrix assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, the fullerene polymers thus obtained possess well-defined structure, narrow polydispersity (∼1.01 by MALDI-TOF mass spectrometry; ∼1.03 by size exclusion chromatography), and high fullerene functionality (∼100%). They can serve as model compounds for the investigations of polymer structures and dynamics.
Co-reporter:Yiwen Li, Wen-Bin Zhang, Jonathan E. Janoski, Xiaopeng Li, Xuehui Dong, Chrys Wesdemiotis, Roderic P. Quirk, and Stephen Z. D. Cheng
Macromolecules 2011 Volume 44(Issue 9) pp:3328-3337
Publication Date(Web):April 14, 2011
DOI:10.1021/ma200364p
A series of precisely defined, mono- and heterotelechelic polystyrenes have been facilely synthesized by combining living anionic polymerization with other efficient chemical transformations, such as thiol–ene “click” chemistry and hydrosilylation reactions, leading to a versatile and general functionalization methodology for chain-end-functionalized anionic polymers. Specifically, α-vinyl-ended poly(styryl)lithiums, which were prepared using 4-pentenyllithium as an initiator under high-vacuum conditions, were reacted with different end-capping reagents using living functionalization methods to afford various chain-end functionalities quantitatively, namely, α-vinylpolystyrene, α-vinyl-ω-hydroxylpolystyrene, and α-vinyl-ω-hydrosilylpolystyrene. Subsequent functionalizations using photoinitiated thiol–ene “click” chemistry and hydrosilylation reactions allow facile and efficient installation of diverse functionalities onto the α- and ω-chain ends of these polymers, respectively, including amine groups, carboxylic acid groups, hydroxyl groups, and perfluorinated alkyl chains. It was found that the heterofunctionalization should be carried out in the sequence of hydrosilylation and then thiol–ene reaction to achieve precisely defined products, probably due to the side products associated with the reaction between silyl hydrides and radical intermediates. The polymers have been thoroughly characterized by 1H NMR, 13C NMR, FT-IR, SEC, and MALDI-TOF mass spectrometry to establish their chemical structures and chain-end functionalities, which indicates precisely defined mono- and heterotelechelic polystyrenes with 100% functionalities. These polymers serve as important model compounds in the study of their bulk properties as well as self-assembling behaviors.
Co-reporter:Yan Cao, Ryan M. Van Horn, Hao-Jan Sun, Guoliang Zhang, Chien-Lung Wang, Kwang-Un Jeong, Finizia Auriemma, Claudio De Rosa, Bernard Lotz, and Stephen Z. D. Cheng
Macromolecules 2011 Volume 44(Issue 10) pp:3916-3923
Publication Date(Web):April 22, 2011
DOI:10.1021/ma102902y
Two high molecular weight (MW) isotactic polypropylene (i-PP) samples, one containing a small amount of rr stereodefects denoted R1 and one conventional, commercial i-PP denoted S1, were used to grow single crystals in thin films at high temperatures (Tx = 145 °C for R1, Tx = 155 °C for S1). Elongated α2-form lathlike single crystals could be found in these two samples, indicating that the growth of this type of single crystal is a general phenomenon in i-PP and is independent of the small amount of tacticity defects. On the basis of our selected area electron diffraction (SAED) experimental results, the stems in these lathlike single crystals were tilted at an unusual 17° angle around the b-axis (i.e., a rotation of 17° of the c-axis within the ac-plane toward the a-axis direction), while in the traditional scheme of the α-form in i-PP, the stem axis is understood to be normal to the fold surface. This 17° stem tilt in the α2-form, lathlike single crystals grown at high Tx values appears to depend upon two constraints: (a) the conformational restrictions on chirality and clinicity of isotactic polyolefin stems linked by a fold, as analyzed by Petraccone et al. [ Polymer 1986, 27, 1665; Eur. Polym. J. 1989, 25, 43], and (b) a minimized encumbrance at the fold surface can be achieved by those folds which start from and end on the chemical bonds normal to the fold surface with a favorable gauche conformation of i-PP chains. This is because in i-PP (and most isotactic polyolefins) with a helical stem conformation every other chemical bond is nearly parallel (in a trans conformation) or perpendicular (in a gauche conformation) to the stem axis (and thus, nearly within or normal to the fold surface). The combination of these two constraints favors a (102̅) fold surface in the i-PP case, as is observed in this study.
Co-reporter:Huiming Xiong, Chun-Ku Chen, Kyungmin Lee, Ryan M. Van Horn, Zheng Liu, Bin Ren, Roderic P. Quirk, Edwin L. Thomas, Bernard Lotz, Rong-Ming Ho, Wen-Bin Zhang, and Stephen Z. D. Cheng
Macromolecules 2011 Volume 44(Issue 19) pp:7758-7766
Publication Date(Web):September 12, 2011
DOI:10.1021/ma201325t
To understand the formation mechanism of nonflat polymer single crystals, two types of triblock copolymers with a middle crystalline block and two amorphous, immiscible end-blocks were designed and synthesized. Specifically, polystyrene-block-poly(ethylene oxide)-block-poly(1-butene oxide) and polystyrene-block-poly(ethylene oxide)-block-polydimethylsiloxane were examined. When the end-blocks possess different volumes and are microphase separated onto the opposite sides of the single crystal lamella formed by the middle crystalline block, unbalanced surface stress can be generated. As a result, large scrolled single crystals (∼80 μm) were grown from dilute solution using the self-seeding procedure at low supercoolings. The scrolling direction was identified to be along the (120) planes based on transmission electron microscopy (TEM) observations of the sedimented scrolled single crystals, which is in line with the fact that the scrolling occurs along the planes with the highest coefficient of thermal expansion. Using high-resolution TEM at high tilting angles, three layers of distinct chemical compositions can be clearly identified from the edges of the single crystals after RuO4 staining. It suggests the formation of microphase separated domains of the amorphous end-blocks on the opposite sides of PEO single crystals. Although the tethering densities of these amorphous end-blocks are identical, their reduced tethering densities are different, resulting in dissimilar volumes and surface crowdedness on the opposite sides of PEO single crystal. The unbalanced surface stress is thus generated to scroll the lamellar single crystal. Macroscopically, based on the observed curvature and the assumption of a solid plate cylinder, the strain energy for each individual single crystal with lateral size of 80 μm was estimated to be ∼3 × 10–9 erg, which, though small, is sufficient to maintain the scrolling of single crystal in solution at room temperature (the thermal energy is approximately kT ∼ 4 × 10–14 erg). Microscopically, the difference of the reduced surface free energy of the tethered blocks at the opposite sides of the PEO lamellar single crystal is analyzed and understood to be the driving force of the scrolling.
Co-reporter:Ian Mann;Xinfei Yu;Wen-Bin Zhang;Ryan M. Van Horn
Chinese Journal of Polymer Science 2011 Volume 29( Issue 1) pp:81-86
Publication Date(Web):2011 January
DOI:10.1007/s10118-010-1022-6
The polymer surface relaxation in thin films has been a long debating issue. We report a new method on studying surface relaxation behaviors of polymer thin films on a solid substrate. This method involved utilizing a rubbed polyimide surface with a pretilting angle in a liquid crystalline cell. Due to the surface alignment, the liquid crystals were aligned along the rubbing direction. During heating the liquid crystalline cell, we continuously monitored the change of orientation of the liquid crystals. It is understood that at a temperature where the orientation of liquid crystal is lost, the surface relaxation on the glass substrate takes place to lose the polyimide surface orientation. It was found that the relaxation temperature at which the liquid crystals lose their orientation depends on the film thickness of the polyimide. A quantitative linear relationship between the relaxation temperature and reciprocal of the film thickness can be observed. Furthermore, different topologies of the rubbed and relaxed thin films were amplified using the polyethylene decoration method and observed using atomic force microscopy.
Co-reporter:Wen-Bin Zhang, Yiwen Li, Xiaopeng Li, Xuehui Dong, Xinfei Yu, Chien-Lung Wang, Chrys Wesdemiotis, Roderic P. Quirk, and Stephen Z. D. Cheng
Macromolecules 2011 Volume 44(Issue 8) pp:2589-2596
Publication Date(Web):March 25, 2011
DOI:10.1021/ma200268u
This paper reports a facile, modular, and efficient approach to the synthesis of shape amphiphiles with a hydrophobic polymer chain as the tail and a polar, compact, functional polyhedral oligomeric silsequioxane (POSS) nanoparticle as the headgroup. A poly(l-lactide) (PLLA) chain was grown from monohydroxyl-functionalized heptavinyl POSS (VPOSS−OH) with controlled molecular weight and narrow polydispersity by stannous octoate-mediated ring-opening polymerization of l-lactide. To impart tunable polarity and functionality to the headgroup, various functional groups, such as carboxylic acids, hydroxyl groups, and sugars, were attached to the POSS cage in high efficiency by thiol−ene “click” chemistry, which provides a straightforward and effective approach to synthesize shape amphiphiles with diverse head surface chemistry. The polymers have been fully characterized by 1H NMR, 13C NMR, FT-IR spectroscopy, MALDI-TOF mass spectrometry, and size exclusion chromatography. These functional POSS can serve as versatile nanobuilding blocks in the “bottom-up” construction of nanoscale structures and assemblies that may exhibit rich self-assembling behavior and potentially useful physical properties.
Co-reporter:Guoliang Zhang, Yan Cao, Liuxin Jin, Ping Zheng, Ryan M. Van Horn, Bernard Lotz, Stephen Z.D. Cheng, Wei Wang
Polymer 2011 Volume 52(Issue 4) pp:1133-1140
Publication Date(Web):17 February 2011
DOI:10.1016/j.polymer.2011.01.002
A low molecular weight (MW) poly(ethylene oxide) (PEO) crystallized in ultrathin films displays various crystal growth patterns in a crystallization temperature (Tx) range from 20.0 °C to 50.0 °C. In succession, the following patterns are found: nearly one-dimensional (1D) dendrite-like crystal patterns at Tx ≤ 38.0 °C, two-dimensional (2D) seaweed-like patterns between 39.0 °C ≤ Tx ≤ 42.0 °C and again, nearly 1D dendrite-like patterns at Tx ≥ 43.0 °C. These transitions result from a complex interplay of varying growth rates along different growth directions and preservation of growth planes. Structural analysis carried out via electron diffraction indicates that the dendrite-like crystals formed at the low and high Tx values differ by their fast growth directions: along the {120} normal at the low Tx values and along the (100) and (010) normal at the high Tx values. In the later case however, the major growth faces are still the {120}, this time tilted at 45° and indicating the a∗ and b axes growth tips. In the intermediate Tx range (39.0 °C–42.0 °C), three growth directions coexist giving rise to the seaweed morphology. The crystal growth rates at the low and high Tx values are constant versus time. For the seaweed, a square-root dependence is obtained. These differences are probably due to 1D and 2D growth in the ultrathin films and are associated with different growth patterns of the dendrites and the seaweed, respectively.
Co-reporter:Xinfei Yu, Sheng Zhong, Xiaopeng Li, Yingfeng Tu, Shuguang Yang, Ryan M. Van Horn, Chaoying Ni, Darrin J. Pochan, Roderic P. Quirk, Chrys Wesdemiotis, Wen-Bin Zhang, and Stephen Z. D. Cheng
Journal of the American Chemical Society 2010 Volume 132(Issue 47) pp:16741-16744
Publication Date(Web):November 4, 2010
DOI:10.1021/ja1078305
A novel giant surfactant possessing a well-defined hydrophilic head and a hydrophobic polymeric tail, polystyrene−(carboxylic acid-functionalized polyhedral oligomeric silsesquioxane) conjugate (PS−APOSS), has been designed and synthesized via living anionic polymerization, hydrosilylation, and thiol−ene “click” chemistry. PS−APOSS forms micelles in selective solvents, and the micellar morphology can be tuned from vesicles to wormlike cylinders and further to spheres by increasing the degree of ionization of the carboxylic acid. The effect of APOSS−APOSS interactions was proven to be essential in the morphological transformation of the micelles. The PS tails in these micellar cores were found to be highly stretched in comparison with those in traditional amphiphilic block copolymers, and this can be explained in terms of minimization of free energy. This novel class of giant surfactants expands the scope of macromolecular amphiphiles and provides a platform for the study of the basic physical principles of their self-assembly behavior.
Co-reporter:Shaohui Lin, Xinfei Yu, Yingfeng Tu, Hongyu Xu, Stephen Z. D. Cheng and Li Jia
Chemical Communications 2010 vol. 46(Issue 24) pp:4273-4275
Publication Date(Web):19 May 2010
DOI:10.1039/C0CC00324G
The titled diblock copolymers are synthesized via cobalt-catalyzed living carbonylative polymerization of N-alkylaziridines under moderate pressures followed by a deprotection step. The poly(β-alanine) block is solubilized by the poly(β-alanoid) block in chloroform and remains fully hydrogen-bonded in the form of a sheet-like assembly.
Co-reporter:Siwei Leng, Li Hsin Chan, Jiaokai Jing, Jie Hu, Rasha M. Moustafa, Ryan M. Van Horn, Matthew J. Graham, Bin Sun, Meifang Zhu, Kwang-Un Jeong, Bilal R. Kaafarani, Wenbin Zhang, Frank W. Harris and Stephen Z. D. Cheng
Soft Matter 2010 vol. 6(Issue 1) pp:100-112
Publication Date(Web):02 Nov 2009
DOI:10.1039/B912634A
It is known that in photovoltaic applications, columnar discotic liquid crystal (LC) phases of conjugated compounds are useful to align the molecules for improving their charge mobilities. However, conjugated compounds are usually either crystalline or amorphous. For compounds to form columnar discotic LC phases, specific molecular design is required for their ordered structural packing. In our recent report, a series of conjugated compounds, 6,7,15,16-tetrakis(alkylthio)quinoxalino-[2′,3′:9,10]-phenanthro[4,5-abc]phenazine (TQPP-[SCn]4) (n = 6, 8, 10 and 12), which display p-channel characteristics, were synthesized and characterized. This series of compounds was crystalline and did not exhibit LC behavior (S. Leng, B. Wex, L. H. Chan, M. J. Graham, S. Jin, A. J. Jing, K.-U. Jeong, R. M. Van Horn, B. Sun, M. Zhu, B. R. Kaafarani and S. Z. D. Cheng, J. Phys. Chem. B, 2009, 113, 5403–5411). In order to create a columnar LC phase with the lowest free energy within a broad applicable temperature region, we specifically designed and synthesized several series of electron-deficient phenazine derivatives to disrupt the molecular crystal packing and force the compounds to enter the columnar LC phase. These phenazine derivatives were designed to control the fused rigid ring size and shape as well as the location, lengths, and chemical structures of their flexible tails. These series include a series of 2,11-bis(1-methylethyl)-6,7,15,16-tetrakis(alkoxy)quinoxalino[2′,3′:9,10]phenanthro-[4,5-abc]-phenazines (TQPP-[t-Bu]2-[OR(B)]4), a series of 2,13-bis(1-methylethyl)-7,8,18,19-tetrakis(alkoxy)pyrazino[2,3-i]pyrazino[2″,3″:6′,7′]quinoxalino[2′,3′:9,10]phenanthro[4,5-abc]-phenazines (TPPQPP-[t-Bu]2-[OR(B)]4), and a series of 3,4,11,12,19,20-hexaalkoxy-2,5,7,8,10,13,15,16,18,21,23,24-dodecaazatri-anthracenes (HDATAN-[OR]6), where R is the alkyl chain in the substituents and B represents that they are branched structures. The different phase structures and transition behaviors of these series of compounds were studied, and based on the experimental results, we can conclude that tailoring the alkyl tail size, the core size, and the core shape leads to a promising way to design molecules that exhibit the columnar LC phase. In particular, changes in alkyl tail architecture affect the phase behaviors more significantly than changes in its length.
Co-reporter:Jing Wang, Christopher Y. Li, Shi Jin, Xin Weng, Ryan M. Van Horn, Matthew J. Graham, Wen-Bin Zhang, Kwang-Un Jeong, Frank W. Harris, Bernard Lotz, and Stephen Z. D. Cheng
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 23) pp:11936-11947
Publication Date(Web):March 26, 2010
DOI:10.1021/ie100248r
Chirality transfer (or amplification) in soft materials is an important topic for understanding how chiral assemblies develop from the atomic level to macroscopic objects. This is an interdisciplinary area which is critically associated with the evolution from asymmetric chemistry to asymmetric physics, and, more specifically, in biomaterials, liquid crystals, and polymers. In this review, we discuss our recent studies on the conditions for chirality transfer across different length scales. We observed that the formation of helical structures in different length scales is a typical process in chirality transfer. This is illustrated by a series of nonracemic chiral main-chain liquid crystalline (LC) polyesters, PETs(R*-n). The polymers contained a different number of methylene units in the chain backbone (from 7 to 11). All of the PETs(R*-n) macroscopically exhibited an LC chiral smectic C (SC*) phase, a chiral smectic A (SA*) phase, and a twist grain boundary smectic A (TGBA*) phase with increasing temperature. The atomic chiral centers caused the helical conformation, and then, helical lamellar crystals were found in these polymers. The crystal structures were determined by X-ray diffraction and electron diffraction techniques. Dark field transmission electron microscopic images revealed that the molecular orientation in these helical crystals is double twisted. Our systematic studies showed that chirality transfer from one length scale to another is neither automatic, nor necessary, and it critically depends upon the packing scheme of the chiral building blocks on each length scale. It was particularly surprising that in this series of polyesters, the odd−even effect exists across many length scales. This includes not only thermodynamic properties such as the SC*, the SA*, and the TGBA* LC phase transition temperatures, but also the helical crystal handedness.
Co-reporter:Xiangkui Ren, Bin Sun, Chi-Chun Tsai, Yingfeng Tu, Siwei Leng, Kaixia Li, Zhuang Kang, Ryan M. Van Horn, Xiaopeng Li, Meifang Zhu, Chrys Wesdemiotis, Wen-Bin Zhang and Stephen Z. D. Cheng
The Journal of Physical Chemistry B 2010 Volume 114(Issue 14) pp:4802-4810
Publication Date(Web):March 25, 2010
DOI:10.1021/jp100126u
A novel organic−inorganic hybrid with two polyhedral oligosilsesquioxane (POSS) nanoparticles covalently attached to perylene diimide (PDI) via a rigid 1,4-phenylene linkage (POSS-PDI-POSS) was designed and synthesized to examine the effect of bulky and well-defined nanoparticle side chains on the self-assembly behavior of PDI derivatives. The molecules were self-assembled directly by slow evaporation of a cast drop from solution in tetrahydrofuran to give rise to uniform crystalline nanobelts with dimensions typically of 0.2 mm × 1 μm × 50 nm. The phase behavior and crystal structure of the sample were then elucidated via a combination of different experimental techniques such as differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), selected area electron diffraction (SAED) in transmission electron microscopy (TEM), polarized light microscopy, and atomic force microscopy. One-dimensional (1D) WAXD and DSC revealed that only one crystalline phase exists. Based on the 2D WAXD fiber pattern obtained from the oriented POSS-PDI-POSS samples, the crystalline structure was determined to be a triclinic unit cell with dimensions of a = 6.577 nm, b = 5.213 nm, c = 1.107 nm, α = 93.26°, β = 94.85°, and γ = 92.73°, which was confirmed by SAED experiments on the single crystals with different crystal zone orientations. The detailed molecular conformational analysis indicated that the steric hindrance of the POSS nanoparticles covalently attached to PDI via a rigid 1,4-phenylene linkage makes it difficult to achieve a continuous stacking of PDIs. Instead, the molecules dimerized to maximize the π−π interaction. The dimers then became the building blocks and packed themselves into the unit cell. This strong tendency for dimerization was supported by concentration-dependent ultraviolet/visible absorption spectra, florescence spectra, and tandem mass spectroscopy with traveling wave ion mobility separation. The combined SAED and TEM results showed that the c*-axis of the crystal is along the elongated direction of the single-crystal nanobelt and the normal direction of the π−π stacking is along the a*-axis. A crystal structure with six dimers as one supramolecular motif in one unit cell was proposed to account for the unusually large unit cell dimensions. The complex structure could be attributed to the longitudinal, transverse, and slightly rotational offsets between the PDIs in the dimers and interdigitated neighboring dimers due probably to both electrostatic interactions and steric demands. The molecular packing scheme in the crystal was simulated using Cerius2 software, and the resulting diffraction data agreed well with the experimental results. The rationale for such 1D nanostructured morphology formation is also discussed.
Co-reporter:Chi-Chun Tsai, Siwei Leng, Kwang-Un Jeong, Ryan M. Van Horn, Chien-Lung Wang, Wen-Bin Zhang, Matthew J. Graham, Jin Huang, Rong-Ming Ho, Yongming Chen, Bernard Lotz, and Stephen Z. D. Cheng
Macromolecules 2010 Volume 43(Issue 22) pp:9454-9461
Publication Date(Web):October 20, 2010
DOI:10.1021/ma101943k
Supramolecular crystals were prepared via self-assembly of a series of inclusion complexes of β-cyclodextrin (β-CD) with poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-b-PPO-b-PEO) block copolymer. In this study, two PEO-b-PPO-b-PEO copolymers were used with different molecular weights for the PEO blocks. On the basis of two-dimensional (2D) wide-angle X-ray diffraction (WAXD) and selected area electron diffraction (SAED) experiments, the supramolecular crystal structure was determined to be a monoclinic lattice with a = 1.910 nm, b = 2.426 nm, c = 1.568 nm, and β = 111° for both inclusion complex systems. Each crystal unit cell contained four inclusion complexes. The space group was identified to be C2 symmetry based on the relationship among diffraction spot intensity and systematic extinctions. With the help of computer simulations of the supramolecular structure, the packing of inclusion complexes in the crystal lattice could be achieved. The simulated 2D WAXD fiber patterns and SAED patterns agreed well with the experimental results. Observations of the morphology in transmission electron microscopy combined with the [001] zone SAED patterns indicated that the supramolecular crystals are lozenge-shaped, bound by four (110) planes. Furthermore, the tethered PEO blocks were found to crystallize, and the c-axis of the PEO crystals was nearly parallel to the lamellar surface normal of the supramolecular crystals. The existence of PEO crystals resulted in additional proof that β-CDs are only selectively threaded onto the PPO blocks when forming the inclusion complexes. These PEO crystals acted as locks to prevent the dethreading of the β-CDs from the complexes and physically stabilized the supramolecular structure.
Co-reporter:Shuguang Yang, Xinfei Yu, Lian Wang, Yingfeng Tu, Joseph X. Zheng, Junting Xu, Ryan M. Van Horn and Stephen Z. D. Cheng
Macromolecules 2010 Volume 43(Issue 6) pp:3018-3026
Publication Date(Web):February 23, 2010
DOI:10.1021/ma902776e
Hydrogen-bonding complexation between spherical diblock copolymer polystyrene-block-poly(ethylene oxide) (PS-b-PEO) micelles and poly(acrylic acid) (PAA) was systematically investigated. We prepared the micelles by gently adding a selective solvent, water, to a PS240-b-PEO182/N,N-dimethylformamide (DMF) solution. After DMF was removed by dialysis, the diluted micelles were associated with PAA at different pH values. The complexation behavior was studied via ultraviolet−visible spectroscopy, laser light scattering, ζ-potential, and transmission electron microscopy techniques. As the pH value varied, the complexation between the PS240-b-PEO182 micelles and PAA behaved differently. At pH < 3.0, the system was in the flocculation region where large aggregates of the micelles formed spontaneously. A single-micelle, stepwise adsorption region could be observed when the pH value was in the range of 3.0−4.8. Above a pH value of 4.8, no adsorption could be found. The value of pH 3.0 was recognized as the onset pH value for the micellar flocculation. At this value, the micelle flocculating rate was very slow, and thus the flocculating process was able to be monitored. A “pearl-necklace-like” morphology at pH 3.0 was observed, and its formation mechanism was also discussed.
Co-reporter:Ryan M. Van Horn, Joseph X. Zheng, Hao-Jan Sun, Ming-Siao Hsiao, Wen-Bin Zhang, Xue-Hui Dong, Junting Xu, Edwin L. Thomas, Bernard Lotz and Stephen Z. D. Cheng
Macromolecules 2010 Volume 43(Issue 14) pp:6113-6119
Publication Date(Web):June 28, 2010
DOI:10.1021/ma1010793
The crystallization behavior of crystalline−crystalline (CC) diblock copolymers has been shown to be dependent on the crystallization temperature and relative molecular size of each component. The behavior of copolymers with similar crystallization temperatures is controlled by the block with the larger weight fraction and solvent−polymer interactions. Using samples of poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL), dilute solution crystallization methods were investigated to determine their role in crystallization of CC copolymers. A single crystal of one block, either PEO or PCL (the first block), crystallized first with the second block segregated to the crystal basal surfaces. For the first time, solvent quality and homopolymer seeds were introduced to manipulate crystallization of the block with the smaller weight fraction to crystallize first and form the lamellar single crystal. In addition, subsequent crystallization of the tethered chains (the second block) on the surface was also observed, depending upon the molecular weight of the second block and crystallization conditions. These crystallites formed by the second block exhibited preferred orientations on the crystal surface as observed by electron diffraction. It is believed that this orientation was induced by “soft” epitaxy between the fold surfaces of the adjacent single crystals of the first block formed by the initial crystallization.
Co-reporter:Shujun Wang, Changjiang Wu, Min-Qiao Ren, Ryan M. Van Horn, Matthew J. Graham, Charles C. Han, Erqiang Chen, Stephen Z.D. Cheng
Polymer 2009 50(4) pp: 1025-1033
Publication Date(Web):
DOI:10.1016/j.polymer.2008.12.028
Co-reporter:Yan Cao, Ryan M. Van Horn, Chi-Chun Tsai, Matthew J. Graham, Kwang-Un Jeong, Bojie Wang, Finizia Auriemma, Claudio De Rosa, Bernard Lotz and Stephen Z. D. Cheng
Macromolecules 2009 Volume 42(Issue 13) pp:4758-4768
Publication Date(Web):May 12, 2009
DOI:10.1021/ma900475h
In the past, the crystallographic relationship between the γ-phase and the α-phase in isotactic polypropylene (i-PP) was extensively studied and established via i-PP oligomers of which the γ-phase can be formed at atmospheric pressure. We attempt to investigate how the epitaxial domination of the crystal morphologies takes place in the γ-phase of chain-folded crystals using high molecular weight i-PP samples with a controlled number of stereodefects. These specifically synthesized samples favor the isothermal growth of the γ-phase crystals from a thin film melt at 100−140 °C at atmospheric pressure. It is known that the γ-phase unit cell has the very unique characteristic of an orthorhombic lattice with alternating stem orientations in every two stem layers along the c-axis. Due to the specific epitaxial growth of the γ-phase on the elongated α-phase single crystals, two different morphologies were identified via transmission electron and atomic force microscopies (TEM and AFM). The first γ-phase crystalline morphology is needle-like. The selected area electron diffraction (SAED) results showed that either the [1̅10] or [110] zone axis was parallel to the thin film normal, and the needle direction was along the c-axis of the γ-phase. The epitaxial growth of this type of γ-phase crystal was generated from the stem direction in the initial α-phase single crystal being parallel to the thin film (and thus, the lamellar) normal. In this case, the stem length of the α-phase single crystal provided a limit for the growth of the γ-phase to develop toward the thin film normal. On the other hand, the stem length oriented at ±80° away from the film normal in the γ-phase crystal was limited by the folded chain crystal growth kinetics, which is proportional to the reciprocal supercooling. These two factors thus resulted in the formation of these peculiar needle-like crystals. The second γ-phase crystalline morphology was “flat” lamellae. The SAED results indicated that the chain orientations in the “flat” lamellae were tilted at ± 40° from the thin film normal within the ab-plane of the γ-phase. Macroscopically, growth of the “flat” lamellae was thermodynamically more stable compared with the needle-like crystals due to their larger crystal size. On the basis of the tilted SAED and dark field results from TEM, the microscopic formation mechanism of this morphology revealed that the initial α-phase single crystal had to have a stem orientation tilted ± 25° away from the thin film normal within the ac-plane around the b-axis. Therefore, the epitaxial growth of the γ-phase on the ac-plane of the α-phase did not possess a chain orientation of ± 40° from the thin film normal. The final “flat” lamellar γ-phase crystals might have resulted from a continuous twist of the chain orientation from +25°/−55° or −25°/+55° to ±40° from the thin film normal.
Co-reporter:Wen-Bin Zhang, Bin Sun, Hui Li, Xiangkui Ren, Jonathan Janoski, Sujata Sahoo, David E. Dabney, Chrys Wesdemiotis, Roderic P. Quirk and Stephen Z. D. Cheng
Macromolecules 2009 Volume 42(Issue 19) pp:7258-7262
Publication Date(Web):September 8, 2009
DOI:10.1021/ma901506d
Co-reporter:Siwei Leng, Brigitte Wex, Li Hsin Chan, Matthew J. Graham, Shi Jin, Alexander J. Jing, Kwang-Un Jeong, Ryan M. Van Horn, Bin Sun, Meifang Zhu, Bilal R. Kaafarani and Stephen Z. D. Cheng
The Journal of Physical Chemistry B 2009 Volume 113(Issue 16) pp:5403-5411
Publication Date(Web):March 30, 2009
DOI:10.1021/jp810653z
A series of conjugated compounds, 6,7,15,16-tetrakis(alkylthio)quinoxalino[2′,3′:9,10]phenanthro[4,5-abc]phenazine (TQPP-[SCn]4) (n = 6, 8, 10, and 12), which display p-channel characteristics was synthesized. These materials show promise for use in liquid crystalline photovoltaic applications. To determine their applicability, the different phase structures and transitions of these compounds were studied with differential scanning calorimetry (DSC), polarized light microscopy (PLM), wide-angle X-ray diffraction (WAXD), selected area electron diffraction (SAED), and Fourier transform infrared spectroscopy (FT-IR). Using TQPP-[SC12]4 as a model compound, DSC and 1D WAXD results showed that this compound possesses four crystalline, but no liquid crystalline, phases. Based on structural results obtained from 2D WAXD experiments on oriented samples and SAED patterns from single crystals, the unit cell of the lowest temperature TQPP-[SC12]4 crystalline phase (K1) was determined to be monoclinic with dimensions of a = 1.87 nm, b = 0.53 nm, c = 3.51 nm, and β = 96.2°. With increasing temperature, the K1 phase transformed to other crystalline phases which all were monoclinic with different crystallographic parameters. The arrangement of the TQPP-[SC12]4 rigid fused rings changed only slightly in these crystalline phases, yet the conformation of the alkyl chains attached to the rigid cores changed significantly at the phase transitions. For the other TQPP-[SCn]4 compounds, only two phase transitions could be identified. It was determined that the transition temperature can be tuned by modifying the attached alkyl chains at the four corners of the rigid fused rings. One-dimensional WAXD studies indicated that the condensed state phase transitions of these compounds were all crystal−crystal transitions. Although single crystals will provide the highest charge carrier mobility, they are very difficult to grow and incur a high cost in production. On the other hand, liquid crystalline phases are preferred for the ease of processing and reasonable performance in change carrier mobility. Therefore, in order to achieve liquid crystalline phases in these compounds, as desired for their application as organic photovoltaic materials, additional modifications to the alkyl chains and their locations are necessary.
Co-reporter:Ming-Siao Hsiao, Joseph X. Zheng, Ryan M. Van Horn, Roderic P. Quirk, Edwin L. Thomas, Hsin-Lung Chen, Bernard Lotz and Stephen Z. D. Cheng
Macromolecules 2009 Volume 42(Issue 21) pp:8343-8352
Publication Date(Web):September 21, 2009
DOI:10.1021/ma901565h
In this study, we systematically investigated the effects of confined dimension (the thickness of PEO layer) and reduced tethering density (σ̃PEO, defined by σπRg2, where σ is the tethered chain density and Rg is the radius of gyration of the tethered PEO chain in its end-free state in the melt) on the PEO crystal orientation change within a 1D nanoscale confinement. We realized this confinement by utilizing two symmetric polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer single crystals grown at different crystallization temperatures (Tx) in dilute solution via the self-seeding technique. After these single crystals were collected as mats, the thicknesses of both the PEO single crystal (dPEO) and PS glassy layer were measured using small-angle X-ray scattering (SAXS) coupled to the 1D correlation function. Because TgPS is higher than TmPEO in those PS-b-PEO single crystal mats, 1D confinements having different dPEO and σ̃PEO values can be prepared by changing Tx values. The PEO block single crystals were melted and recrystallized at different temperatures (Trx), and the c-axis orientation of the recrystallized PEO crystals with respect to glassy PS layers at different Trx values can be monitored by simultaneous 2D SAXS and WAXD techniques. Two observations of the PEO crystal orientation were found in these PS-b-PEO mats. First, three different c-axis orientations of the PEO crystals with respect to the PS layer normal were observed: random, homogeneous, and approximately homeotropic. Second, a dramatic change from homogeneous to homeotropic takes place within a few degrees Celsius. The onset temperature of this orientation change (Tonset) decreases with increasing dPEO and σ̃PEO values. The Tonset values were found to lie within a temperature range of nearly 20 °C (from 0 to −19 °C). Mechanisms of the confined dimension and reduced tethering density effects on determining those Tonset values are proposed.
Co-reporter:Bernard Lotz and Stephen Z D Cheng
Polymer Journal 2008 40(9) pp:891-899
Publication Date(Web):May 21, 2008
DOI:10.1295/polymj.PJ2008029
A critical analysis is presented regarding the possible processes that determine polymer crystal growth, based mostly on the analysis of the structure and morphology of polymer single crystals. This “forensic” analysis suggests that the interaction of the depositing stem with the growth front is the determining factor in the whole crystallization process, irrespective of any previous (pre)organization process, be it spinodal decomposition, formation of “smectic pearls” or precursor phases followed by local reorganization. This conclusion stems from the analysis of the structure and morphology of polymer single crystals, from the recognition that bulk crystallization leads to similar structures of the lamellae that build up the spherulites, and from the distinctly different structures and morphologies of polymers for which a precursor phase (with either smectic or nematic order) has been recognized. The latter situation, with an intermediate loose pre-order, prevails for polymers with inherent chain rigidity.
Co-reporter:Ming-Siao Hsiao, William Y. Chen, Joseph X. Zheng, Ryan M. Van Horn, Roderic P. Quirk, Dimitri A. Ivanov, Edwin L. Thomas, Bernard Lotz and Stephen Z. D. Cheng
Macromolecules 2008 Volume 41(Issue 13) pp:4794-4801
Publication Date(Web):June 6, 2008
DOI:10.1021/ma8006619
A new approach was designed to study polymer crystallization in a one-dimensional (1D), defect-free, nanoscale confinement utilizing single crystals of poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymers as templates. The single crystals grown in dilute solution consisted of a PEO single crystal layer sandwiched between two PS layers formed by the tethered PS blocks on the PEO single crystal top and bottom basal surfaces. Transition behaviors of PEO-b-PS single crystals were investigated using differential scanning calorimetry, transmission electron microscopy, and atomic force microscopy. It was observed that the glass transition temperature of PS blocks in a thin film with a thickness of 7.2 nm is 71 °C, which is higher than the melting temperature of a PEO single crystal with a thickness of 7.9 nm (57 °C). Therefore, the PEO single crystal could be melted, and the PEO blocks could recrystallize in between these two vitrified PS layers when the temperature is brought down to generate sufficient supercooling. This recrystallization process of the PEO blocks was thus carried out in a 1D lamellar confinement without any defects. After the recrystallization, the crystal orientation change of the PEO crystals at different recrystallization temperatures (Trx) was monitored using electron diffraction (ED). First, it was found that the PEO blocks could not recrystallize at Trx > −5 °C, indicating absence of heterogeneous nucleation in the PEO blocks. This Trx of −5 °C corresponds to the starting temperature for homogeneous nucleation of PEO as reported previously. Second, crystallographic analyses of the ED obtained from the recrystallized PEO blocks show that for Trx < −20 °C the c-axis, and thus the PEO small crystals, possess a random orientation. When −20 °C ≤ Trx < −5 °C, the c-axis of the PEO crystals is parallel to the glassy PS basal plane and aligned with the a*- or b-axis of the original PEO-b-PS single crystal grown in dilute solution. The self-seeding technique was used for Trx > −5 °C to create heterogeneous nucleation. Here, the c-axis of PEO crystals was inclined with respect to the vitrified PS lamellar normal at an angle of about 26°.
Co-reporter:Ming-Siao Hsiao, Joseph X. Zheng, Siwei Leng, Ryan M. Van Horn, Roderic P. Quirk, Edwin L. Thomas, Hsin-Lung Chen, Benjamin S. Hsiao, Lixia Rong, Bernard Lotz and Stephen Z. D. Cheng
Macromolecules 2008 Volume 41(Issue 21) pp:8114-8123
Publication Date(Web):October 10, 2008
DOI:10.1021/ma801641w
Utilizing crystalline−amorphous block copolymers, such as in the case of polystyrene-block-poly(ethylene oxide) (PS-b-PEO), under a large amplitude shear process provides an opportunity for investigating crystal growth and orientation within nanoconfinements at different supercoolings. However, the internal stress generated during the shearing process and the structural defects embedded in the phase-separated morphology inevitably play roles in affecting the confinement effect on the crystallization of the crystalline blocks. In this study, we designed a one-dimensional (1D), defect-free confinement constructed by PS-b-PEO single crystal mats collected in dilute solution. Each single crystal possessed a square-shaped, “sandwiched” lamellar structure, and it consisted of a PEO single crystal layer between two PS nanolayers formed by the tethered PS blocks on the PEO single crystal top and bottom fold surfaces. Furthermore, in these single crystal mats the glass transition temperature of the PS blocks is higher than the melting temperature of the PEO single crystals. We melted the PEO crystals between the two vitrified PS nanolayers, and the PEO blocks were recrystallized isothermally by quenching the mats to preset recrystallization temperatures (Trx). The orientation change of the PEO crystals with respect to the “sandwiched” lamellar normal at different Trx values was investigated via 2D small-angle and wide-angle X-ray scattering experiments. It was observed that the PEO c-axis orientation underwent a sharp change from homogeneous (perpendicular to the lamellar normal) in the low Trx region to approximately homeotropic (parallel to the lamellar normal) in the high Trx region. The results showed that this change of the PEO crystal orientation takes place within a few degrees Celsius. Microscopically, the crystal orientation might be determined from the status of critical nuclei formation due to the size and shape of this 1D confinement. This likely included a competition between the high tethering density (the junctions) of the PEO blocks at the PS interfaces leading to the homeotropic orientation with an anisotropic conformational orientation of the PEO blocks in the melt and the anisotropic density fluctuations within the 1D confined layer which could lead to an anisotropic ability for the PEO blocks to overcome the nucleation barrier to form the homogeneous orientation. The resolution of these two factors might explain the origin of the crystal orientation change in 1D confined crystallization. Analysis of the apparent crystallite size in these mats along both the orthogonally oriented [120] directions of the PEO crystals after recrystallization indicated that a change in the PEO crystal growth dimension from 1D to 2D occurs within this narrow Trx region corresponding to the location of the crystal orientation change.
Co-reporter:K.-U. Jeong;D.-K. Yang;M. J. Graham;S.-W. Kuo;B. S. Knapp;Y. Tu;S. Z. D. Cheng;F. W. Harris
Advanced Materials 2006 Volume 18(Issue 24) pp:3229-3232
Publication Date(Web):11 DEC 2006
DOI:10.1002/adma.200601338
Chiral propeller architectures (see figure and inside cover) are constructed from achiral molecules via hydrogen bonding self-assembly in addition to Frank–Pryce spherulitic droplet and fingerprint textures. It is found, for the first time, that neither molecular chirality nor a molecular bend is necessary to form a chiral phase. This is of particular interest to the next generation of biological and electro-optical advances in materials science and technology.
Co-reporter:S.-W. Kuo;D.-K. Yang;B. S. Knapp;Y. Tu;M. J. Graham;S. Z. D. Cheng;K.-U. Jeong;F. W. Harris
Advanced Materials 2006 Volume 18(Issue 24) pp:
Publication Date(Web):18 DEC 2006
DOI:10.1002/adma.200690106
Chiral propeller architectures constructed from achiral molecules via hydrogen bonding self-assembly, in addition to Frank–Pryce spherulitic droplet and fingerprint textures, are reported on p. 3229 by Cheng and co-workers. It is found, for the first time, that neither molecular chirality nor a molecular bend is necessary to form a chiral phase, which is of particular interest for next-generation biological and electro-optical materials science and technology.
Co-reporter:Hong Shen, Kwang-Un Jeong, Huiming Xiong, Matthew J. Graham, Siwei Leng, Joseph X. Zheng, Huabing Huang, Mingming Guo, Frank W. Harris and Stephen Z. D. Cheng
Soft Matter 2006 vol. 2(Issue 3) pp:232-242
Publication Date(Web):01 Feb 2006
DOI:10.1039/B516557A
A series of symmetrically tapered 1,4-bis[3,4,5-tris(alkan-1-yloxy)benzamido] benzene bisamides (CnPhBA, where n is the number of carbon atoms in the alkyl chains, n = 10, 12 and 16), was synthesized in order to investigate the effect of alkyl chain length on supra-molecular ordered structures induced by hydrogen (H)-bonding and micro-phase separation. These bisamides consist of a rigid aromatic bisamide core with three flexible alkyl chains at each end of the core. Major phase transitions and their origins in CnPhBA bisamides were studied with differential scanning calorimetry, one-dimensional (1D) wide angle X-ray diffraction (WAXD), infrared spectroscopy, and solid-state carbon-13 nuclear magnetic resonance experiments. The structures of these compounds in different phases were identified using 2D WAXD from oriented samples and were also confirmed by selected area electron diffractions in transmission electron microscopy from stacked single crystals and by computer simulations. All of the CnPhBA bisamides in this series formed a highly ordered oblique columnar (ΦOK) phase and a low-ordered oblique columnar (ΦOB) phase, similar to a recent report on C14PhBA. The two main driving forces in the formation of these two supra-molecular columnar structures were identified: One was the H-bond formation between N–H and CO groups, and the other was the micro-phase separation between the bisamide cores and the alkyl chains. With increasing the length of alkyl tails, the isotropization temperature decreased, while the disordering temperature of the alkyl tails increased. The 2D lattice structures perpendicular to the columnar axis also increasingly deviated from the pseudo-hexagonal packing with increasing the alkyl tail length. However, the alkyl tail length did not have a significant influence on the packing along the columnar axis direction. Utilizing polarized optical microscopy, the phase identifications were also supported by the observation of texture changes and molecular arrangements inside of the micro-sized domains.
Co-reporter:Joseph X. Zheng;Roderic P. Quirk;Prachur Bhargava
Journal of Polymer Science Part B: Polymer Physics 2006 Volume 44(Issue 24) pp:3605-3611
Publication Date(Web):8 NOV 2006
DOI:10.1002/polb.21002
We report the formation of a highly entangled and interconnected, self-assembled, wormlike-cylinder network of polystyrene-block-poly(ethylene oxide) in N, N-dimethylformamide/water. In this system, N,N-dimethylformamide was a common solvent and water was a selective solvent for the poly(ethylene oxide) blocks. The degrees of polymerization of the polystyrene and poly(ethylene oxide) blocks were 962 and 227, respectively. The network was formed at copolymer concentrations higher than 0.4 wt % and consisted of self-assembled, wormlike cylinders that were interconnected by Y-shaped, T-shaped, and multiple junctions. The network morphology was visualized with transmission electron microscopy. Capillary viscometry measurements revealed an order-of-magnitude increase in the inherent viscosity of the colloidal system upon the formation of the network. A similar effort to obtain a wormlike-cylinder network in an N,N-dimethylformamide/acetonitrile system, in which acetonitrile was a selective solvent for the poly(ethylene oxide) blocks, was unsuccessful even at high copolymer concentrations; instead, the wormlike cylinders showed a tendency to align. The viscosity measurements also did not show a substantial increase in the inherent viscosity. Thus, the solvent played a critical role in determining the formation of the self-assembled, wormlike-cylinder network. This formation of the network resulted from an interplay between the end-capping energy, bending energy (curvature), and configurational entropy of the self-assembled, wormlike-cylinder micelles that minimized the free energy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3605–3611, 2006
Co-reporter:Stephen Z. D. Cheng
Journal of Polymer Science Part B: Polymer Physics 2005 Volume 43(Issue 23) pp:3361-3364
Publication Date(Web):13 OCT 2005
DOI:10.1002/polb.20636
Co-reporter:J.J. Ge;S.-C. Hong;B.Y. Tang;C.Y. Li;D. Zhang;F. Bai;B. Mansdorf;F.W. Harris;D. Yang;Y.-R. Shen;S.Z.D. Cheng
Advanced Functional Materials 2003 Volume 13(Issue 9) pp:
Publication Date(Web):1 SEP 2003
DOI:10.1002/adfm.200304365
Ultraviolet (UV) polymerizable discotic liquid-crystalline (DLC) molecules (2,3,6,7,10,11-hexakis(4′-acryloy-m-alkyloxybenzoyoxy)triphenylene [HAHBT-m, where m was the number of methylene units, and here m = 6 (HAHBT-6)]) were assembled to form a negative retardation film with an oblique optical axis on a specifically designed rubbing-aligned polyimide layer surface [6FDA-11CBBP (where 11 is the number of methylene units in the side chains)]. The side chains of this polyimide were terminated by cyanobiphenyl groups. Surface-enhanced Raman scattering (SERS) and optical second harmonic generation results showed that rubbing caused a surface structural re-arrangement in the alignment layer resulting in a negative pre-tilt angle (θs) of –8.5° (which was in the direction opposite to the rubbing direction). The molecular topology at the rubbed surface was governed by a stable fold-like bent structure of the cyanobiphenyl side chains, in which the CN groups preferentially pointed down towards the surface. When the DLC molecules were deposited onto the alignment surface and polymerized via UV irradiation to generate a new optical film, an oblique optical axis with an average tilt angle of –18.6° with respect to the film normal was detected using ellipsometric measurements. This tilted optical axis was developed by the DLC molecules being wedged on top of the cyanobiphenyl groups when in the bent conformation. Furthermore, the tilt angle difference between the θs at the alignment surface and at the air interface of the DLC molecules was attributed to a splay deformation of the DLC molecules along the film surface normal. Optical modeling has also confirmed our experimental observations.
Co-reporter:S. Jin;S. Cong;G. Xue;H. Xiong;B. Mansdorf;S.Z.D. Cheng
Advanced Materials 2002 Volume 14(Issue 20) pp:
Publication Date(Web):21 OCT 2002
DOI:10.1002/1521-4095(20021016)14:20<1492::AID-ADMA1492>3.0.CO;2-A
Co-reporter:Shaohui Lin, Xinfei Yu, Yingfeng Tu, Hongyu Xu, Stephen Z. D. Cheng and Li Jia
Chemical Communications 2010 - vol. 46(Issue 24) pp:NaN4275-4275
Publication Date(Web):2010/05/19
DOI:10.1039/C0CC00324G
The titled diblock copolymers are synthesized via cobalt-catalyzed living carbonylative polymerization of N-alkylaziridines under moderate pressures followed by a deprotection step. The poly(β-alanine) block is solubilized by the poly(β-alanoid) block in chloroform and remains fully hydrogen-bonded in the form of a sheet-like assembly.
Co-reporter:Hao-Jan Sun, Yingfeng Tu, Chien-Lung Wang, Ryan M. Van Horn, Chi-Chun Tsai, Matthew J. Graham, Bin Sun, Bernard Lotz, Wen-Bin Zhang and Stephen Z. D. Cheng
Journal of Materials Chemistry A 2011 - vol. 21(Issue 37) pp:NaN14247-14247
Publication Date(Web):2011/05/14
DOI:10.1039/C1JM10954E
A shape amphiphile composed of covalently linked spherical and cubic nanoparticles with distinct symmetry ([60]fullerene (C60) and polyhedral oligomeric silsesquioxane (POSS)) was synthesized and its solid state structures were characterized. The two types of nanoparticles are known to be generally immiscible, but they were connected with a short covalent linkage forming an organic–inorganic dyad (POSS–C60) which exhibited interesting crystallization characteristics. Crystals of the dyad exhibited polymorphism with two different crystal structures: an orthorhombic and a hexagonal unit cell with symmetry groups of P21212 and P6, respectively, both of which formed an alternating bi-layered structure of POSS and C60. The different symmetry groups in the polymorphs were attributed to the different packing orientations of the POSS within each layer. In the orthorhombic unit cell, one set of the edges of the POSS moieties is parallel to the c-axis; while in the hexagonal unit cells the body-diagonal is parallel to the c-axis of the crystal. Based on the crystal packing structure and density differential, it has been determined that the hexagonal unit cell structure is the more thermodynamically stable phase. This type of bi-layered structure with an alternating conductive fullerene and insulating POSS layer structure is of great interest for various potential applications such as nano-capacitors.
Co-reporter:Yiwen Li, Kai Guo, Hao Su, Xiaopeng Li, Xueyan Feng, Zhao Wang, Wei Zhang, Sunsheng Zhu, Chrys Wesdemiotis, Stephen Z. D. Cheng and Wen-Bin Zhang
Chemical Science (2010-Present) 2014 - vol. 5(Issue 3) pp:NaN1053-1053
Publication Date(Web):2013/11/18
DOI:10.1039/C3SC52718B
The convenient synthesis of nano-building blocks with strategically placed functional groups constitutes a fundamental challenge in nano-science. Here, we describe the facile preparation of a library of mono- and di-functional (containing three isomers) polyhedral oligomeric silsesquioxane (POSS) building blocks with different symmetries (C3v, C2v, and D3d) using thiol-ene chemistry. The method is straightforward and general, possessing many advantages including minimum set-up, simple work-up, and a short reaction time (about 0.5 h). It facilitates the precise introduction of a large variety of functional groups to desired sites of the POSS cage. The yields of the monoadducts increase significantly using stoichiometric amounts of bulky ligands. Regio-selective di-functionalization of the POSS cage was also attempted using bulky thiol ligands, such as a thiol-functionalized POSS. Electrospray ionization (ESI) mass spectrometry coupled with travelling wave ion mobility (TWIM) separation revealed that the majority of diadducts are para-compounds (∼59%), although meta-compounds (∼20%) and ortho-compounds (∼21%) are also present. Therefore, the thiol-ene reaction provides a robust approach for the convenient synthesis of mono-functional POSS derivatives and, potentially, of regio-selective multi-functionalized POSS derivatives as versatile nano-building blocks.
Co-reporter:Zhao Wang, Yiwen Li, Xue-Hui Dong, Xinfei Yu, Kai Guo, Hao Su, Kan Yue, Chys Wesdemiotis, Stephen Z. D. Cheng and Wen-Bin Zhang
Chemical Science (2010-Present) 2013 - vol. 4(Issue 3) pp:NaN1352-1352
Publication Date(Web):2013/01/25
DOI:10.1039/C3SC22297G
This paper reports our recent investigations in the synthesis, characterization, and solution self-assembly of giant gemini surfactants consisting of two hydrophilic carboxylic acid-functionalized polyhedral oligomeric silsesquioxane (APOSS) heads and two hydrophobic polystyrene (PS) tails covalently linked via a rigid spacer (p-phenylene or biphenylene) (PS–(APOSS)2–PS). The sequential “click” approach was employed in the synthesis, which involved thiol–ene mono-functionalization of vinyl-functionalized POSS, Cu(I)-catalyzed Huisgen [3 + 2] azide–alkyne cycloadditions for “grafting” polymer tails onto the POSS cages, and subsequent thiol–ene “click” surface functionalization. The study of their self-assembly in solution revealed a morphological transition from vesicles to wormlike cylinders and further to spheres as the degree of ionization of the carboxylic acid groups on POSS heads increases. It was found that the PS tails are generally less stretched in the micellar cores of these giant gemini surfactants than those of the corresponding single-tailed (APOSS–PS) giant surfactant. It was further observed that the PS tail conformations in the micelles were also affected by the length of the rigid spacers where the one with longer spacer exhibits even more stretched PS tail conformation. Both findings could be explained by the topological constraint imposed by the short rigid spacer in PS–(APOSS)2–PS gemini surfactants. This constraint effectively increases the local charge density and leads to an anisotropic head shape that requires a proper re-distribution of the APOSS heads on the micellar surface to minimize the total electrostatic repulsive free energy. The study expands the scope of giant molecular shape amphiphiles and has general implications in the basic physical principles underlying their solution self-assembly behaviors.
Co-reporter:Yang Chu, Wei Zhang, Xinlin Lu, Gaoyan Mu, Baofang Zhang, Yiwen Li, Stephen Z. D. Cheng and Tianbo Liu
Chemical Communications 2016 - vol. 52(Issue 56) pp:NaN8690-8690
Publication Date(Web):2016/06/15
DOI:10.1039/C6CC04567G
A series of multi-headed giant surfactants based on polystyrene (PS)-polyhedral oligomeric silsesquioxane(s) (POSS) conjugates, with a different number and topology of POSS heads, are found to self-assemble into different supramolecular structures including vesicles, cylindrical and spherical micelles in H2O/DMF mixed solvents. The transitions among different morphologies can be rationally controlled by tuning the number and topology of POSS heads, as well as the macromolecular concentration.
![Pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane, 1-ethenyl-3,5,7,9,11,13,15-heptakis(2-methylpropyl)-](/data/chemimg/65400/444315-18-8.png)
![Pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane, 1-ethenyl-3,5,7,9,11,13,15-heptakis(2-methylpropyl)-](/data/chemimg/65400/444315-18-8_b.png)
![Benzoic acid, 4-azido-, 2-[[2-[[3-[3-[3,5,7,9,11,13,15-heptakis[3-[(1-oxo-2-propen-1-yl)oxy]propyl]pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl]propoxy]-3-oxopropyl]thio]acetyl]oxy]ethyl ester](/data/chemimg/3783100/1801407-89-5.png)
![Benzoic acid, 4-azido-, 2-[[2-[[3-[3-[3,5,7,9,11,13,15-heptakis[3-[(1-oxo-2-propen-1-yl)oxy]propyl]pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl]propoxy]-3-oxopropyl]thio]acetyl]oxy]ethyl ester](/data/chemimg/3783100/1801407-89-5_b.png)
![Acetic acid, 2-[[2-(3,5,7,9,11,13,15-heptaethenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl)ethyl]thio]-](/data/chemimg/3783000/1588948-21-3.png)
![Acetic acid, 2-[[2-(3,5,7,9,11,13,15-heptaethenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl)ethyl]thio]-](/data/chemimg/3783000/1588948-21-3_b.png)
![1,2-Propanediol, 3,3',3'',3''',3'''',3''''',3'''''',3'''''''-[pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1,3,5,7,9,11,13,15-octayloctakis(2,1-ethanediylthio)]octakis-](/data/chemimg/3783300/1447363-18-9.png)
![1,2-Propanediol, 3,3',3'',3''',3'''',3''''',3'''''',3'''''''-[pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1,3,5,7,9,11,13,15-octayloctakis(2,1-ethanediylthio)]octakis-](/data/chemimg/3783300/1447363-18-9_b.png)
![Acetic acid, 2,2',2'',2''',2'''',2''''',2'''''',2'''''''-[pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1,3,5,7,9,11,13,15-octayloctakis(2,1-ethanediylthio)]octakis-](/data/chemimg/3783300/1446238-68-1.png)
![Acetic acid, 2,2',2'',2''',2'''',2''''',2'''''',2'''''''-[pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1,3,5,7,9,11,13,15-octayloctakis(2,1-ethanediylthio)]octakis-](/data/chemimg/3783300/1446238-68-1_b.png)
![Thieno[3,4-b]thiophene-2-carboxylic acid, 4,6-dibromo-3-fluoro-, 2-ethylhexyl ester](/data/chemimg/1642600/1237479-38-7.png)
![Thieno[3,4-b]thiophene-2-carboxylic acid, 4,6-dibromo-3-fluoro-, 2-ethylhexyl ester](/data/chemimg/1642600/1237479-38-7_b.png)
![Anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10(2H,9H)-tetrone, 2,9-bis[4-[3,5,7,9,11,13,15-heptakis(2-methylpropyl)pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl]phenyl]-](/data/chemimg/3783500/1222472-02-7.png)
![Anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10(2H,9H)-tetrone, 2,9-bis[4-[3,5,7,9,11,13,15-heptakis(2-methylpropyl)pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl]phenyl]-](/data/chemimg/3783500/1222472-02-7_b.png)
![2-Propenoic acid, 1,1',1'',1''',1'''',1''''',1'''''',1'''''''-(pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1,3,5,7,9,11,13,15-octaylocta-3,1-propanediyl) ester](/data/chemimg/3783300/1204591-17-2.png)
![2-Propenoic acid, 1,1',1'',1''',1'''',1''''',1'''''',1'''''''-(pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1,3,5,7,9,11,13,15-octaylocta-3,1-propanediyl) ester](/data/chemimg/3783300/1204591-17-2_b.png)
![Thieno[3,4-b]thiophene-2-carboxylic acid, 4,6-dibromo-, 2-ethylhexyl ester](/data/chemimg/189600/1160823-81-3.png)
![Thieno[3,4-b]thiophene-2-carboxylic acid, 4,6-dibromo-, 2-ethylhexyl ester](/data/chemimg/189600/1160823-81-3_b.png)
![Propanoic acid, 2-[[(dodecylthio)thioxomethyl]thio]-2-methyl-, ethyl ester](/data/chemimg/3730200/1082503-06-7.png)
![Propanoic acid, 2-[[(dodecylthio)thioxomethyl]thio]-2-methyl-, ethyl ester](/data/chemimg/3730200/1082503-06-7_b.png)
![Di-tert-butyl 3,6-bis(5-bromothiophen-2-yl)-1,4-dioxopyrrolo[3,4-c] pyrrole-2,5(1H,4H)-dicarboxylate](http://img.cochemist.com/ccimg/1046900/1046864-84-9.png)
![Di-tert-butyl 3,6-bis(5-bromothiophen-2-yl)-1,4-dioxopyrrolo[3,4-c] pyrrole-2,5(1H,4H)-dicarboxylate](http://img.cochemist.com/ccimg/1046900/1046864-84-9_b.png)
![Di-tert-butyl 1,4-dioxo-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-2,5(1h,4h)-dicarboxylate](http://img.cochemist.com/ccimg/1046900/1046864-83-8.png)
![Di-tert-butyl 1,4-dioxo-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-2,5(1h,4h)-dicarboxylate](http://img.cochemist.com/ccimg/1046900/1046864-83-8_b.png)
![Benzoic acid, 3,4,5-tris[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]-](/data/chemimg/192400/1008460-19-2.png)
![Benzoic acid, 3,4,5-tris[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]-](/data/chemimg/192400/1008460-19-2_b.png)
![Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]](/data/chemimg/102300/920515-34-0.png)
![Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]](/data/chemimg/102300/920515-34-0_b.png)
![Benzenamine, 4-[3,5,7,9,11,13,15-heptakis(2-methylpropyl)pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl]-](/data/chemimg/3783700/875588-35-5.png)
![Benzenamine, 4-[3,5,7,9,11,13,15-heptakis(2-methylpropyl)pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl]-](/data/chemimg/3783700/875588-35-5_b.png)
![Pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1-propanethiol, 3,5,7,9,11,13,15-heptakis(2-methylpropyl)-](/data/chemimg/68400/480438-85-5.png)
![Pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1-propanethiol, 3,5,7,9,11,13,15-heptakis(2-methylpropyl)-](/data/chemimg/68400/480438-85-5_b.png)
![1,4-BENZENEDICARBOXYLIC ACID, 2,5-BIS[(4-BROMOPHENYL)AMINO]-](http://img.cochemist.com/ccimg/477900/477880-89-0.png)
![1,4-BENZENEDICARBOXYLIC ACID, 2,5-BIS[(4-BROMOPHENYL)AMINO]-](http://img.cochemist.com/ccimg/477900/477880-89-0_b.png)
![4-Pentynoic acid, 4'-cyano[1,1'-biphenyl]-4-yl ester](http://img.cochemist.com/ccimg/204500/204451-02-5.png)
![4-Pentynoic acid, 4'-cyano[1,1'-biphenyl]-4-yl ester](http://img.cochemist.com/ccimg/204500/204451-02-5_b.png)
![1,4-Cyclohexadiene-1,4-dicarboxylic acid,2,5-bis[(4-bromophenyl)amino]-, dimethyl ester](http://img.cochemist.com/ccimg/162400/162319-80-4.png)
![1,4-Cyclohexadiene-1,4-dicarboxylic acid,2,5-bis[(4-bromophenyl)amino]-, dimethyl ester](http://img.cochemist.com/ccimg/162400/162319-80-4_b.png)
![[60]PCBA](/data/chemimg/110100/161196-26-5.png)
![[60]PCBA](/data/chemimg/110100/161196-26-5_b.png)
![3,6-bis(4-bromophenyl)-2,5-dihydro-Pyrrolo[3,4-c]pyrrole-1,4-dione](/data/chemimg/1637500/84632-54-2.png)
![3,6-bis(4-bromophenyl)-2,5-dihydro-Pyrrolo[3,4-c]pyrrole-1,4-dione](/data/chemimg/1637500/84632-54-2_b.png)
![QUINO[2,3-B]ACRIDINE-7,14-DIONE, 2,9-DIBROMO-5,12-DIHYDRO-](http://img.cochemist.com/ccimg/52100/52000-71-2.png)
![QUINO[2,3-B]ACRIDINE-7,14-DIONE, 2,9-DIBROMO-5,12-DIHYDRO-](http://img.cochemist.com/ccimg/52100/52000-71-2_b.png)
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2.png)
![Poly[oxy[(1S)-1-methyl-2-oxo-1,2-ethanediyl]]](http://img.cochemist.com/ccimg/26200/26161-42-2_b.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4.png)
![Poly[oxy(1-oxo-1,6-hexanediyl)]](http://img.cochemist.com/ccimg/25300/25248-42-4_b.png)
![Poly[imino(1-oxo-1,3-propanediyl)]](http://img.cochemist.com/ccimg/25000/24937-14-2.png)
![Poly[imino(1-oxo-1,3-propanediyl)]](http://img.cochemist.com/ccimg/25000/24937-14-2_b.png)
![Butanedioic acid, 1-[2-[3,5,7,9,11,13,15-heptakis[2-[(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-hexadecafluorodecyl)thio]ethyl]pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl]ethyl] 4-(2-propyn-1-yl) ester](/data/chemimg/3783000/1623813-18-2.png)
![Butanedioic acid, 1-[2-[3,5,7,9,11,13,15-heptakis[2-[(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-hexadecafluorodecyl)thio]ethyl]pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl]ethyl] 4-(2-propyn-1-yl) ester](/data/chemimg/3783000/1623813-18-2_b.png)
![Butanedioic acid, 1-(11,12-didehydro-5,6-dihydrodibenzo[a,e]cycloocten-5-yl) 4-[2-[(4-formylbenzoyl)oxy]-1-[[[2-(3,5,7,9,11,13,15-heptaethenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl)ethyl]thio]methyl]ethyl] ester](/data/chemimg/3783000/1478782-00-1.png)
![Butanedioic acid, 1-(11,12-didehydro-5,6-dihydrodibenzo[a,e]cycloocten-5-yl) 4-[2-[(4-formylbenzoyl)oxy]-1-[[[2-(3,5,7,9,11,13,15-heptaethenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl)ethyl]thio]methyl]ethyl] ester](/data/chemimg/3783000/1478782-00-1_b.png)
![Pentacyclo[9.5.1.13,?9.15,?15.17,?13]?octasiloxane, 1-?(3-?azidopropyl)?-?3,?5,?7,?9,?11,?13,?15-?heptakis(2-?methylpropyl)?-](/data/chemimg/3781100/1191274-26-6.png)
![Pentacyclo[9.5.1.13,?9.15,?15.17,?13]?octasiloxane, 1-?(3-?azidopropyl)?-?3,?5,?7,?9,?11,?13,?15-?heptakis(2-?methylpropyl)?-](/data/chemimg/3781100/1191274-26-6_b.png)
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![4-Pentynoic acid, 2-(3,5,7,9,11,13,15-heptaethenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl)ethyl ester](/data/chemimg/3783000/1402130-70-4.png)
![4-Pentynoic acid, 2-(3,5,7,9,11,13,15-heptaethenylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxan-1-yl)ethyl ester](/data/chemimg/3783000/1402130-70-4_b.png)
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