Wei Zhang

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Name: 张伟; Wei Zhang

Organization: Soochow University , China

Department: College of Chemistry

Title: Professor(PhD)

TOPICS

Material Chemistry

Polymer

Polymer Brush Covalent Organic Framework Stimuli Responsive Polymers Polyfluorene Atom Transfer Radical Polymerization Hyperbranched Polymers RAFT Polyfluorene Stimuli Responsive Polymers Photo Responsive Polymers

Organic Chemistry

suzuki-miyaura Coupling

Chemicals
References

Fabrication of chiroptically switchable films via co-gelation of a small chiral gelator with an achiral azobenzene-containing polymer

Co-reporter:Dong Yang;Li Zhang;Lu Yin;Yin Zhao;Minghua Liu

Soft Matter (2005-Present) 2017 vol. 13(Issue 36) pp:6129-6136

Publication Date(Web):2017/09/20

DOI:10.1039/C7SM00935F

Helical polymers are widely found in nature and synthetic functional materials. Although a number of elaborate strategies have been developed to endow polymers with helicity through either covalent bonds or supramolecular techniques, it still remains a challenge to get the desired helical polymers with controlled handedness in an easy but effective manner. In this study, we report an easily accessible gelation-guided self-assembly system where the chirality of a gelator can be easily transferred to an achiral azobenzene-containing polymer during gelation. It is found that during the process of chiral induction, the induced chirality of the polymer was entirely dominated by the molecular chirality of the gelator. Experimentally, achiral azobenzene-containing polymers with different side-chain lengths were doped into a supramolecular gel system formed with amphiphilic N,N′-bis-(octadecyl)-L(D)-Boc-glutamic (LBG-18 or DBG-18 for short). CD spectra and SEM observation confirmed that the co-assembly of polymer/LBG-18 or polymer/DBG-18 in the xerogel state exhibited supramolecular chirality. More importantly, alternate UV and visible light irradiation on the xerogel film caused the induced CD signal to switch between on and off states. Thus a chiroptical switch was fabricated based on the isomerization of the azo-polymer in xerogel films.

Rapid limonene-induced mirror symmetry breaking in achiral polyfluorene containing pendant crown ether groups: Enhanced by ion complexation

Co-reporter:Jingjing Liu, Yin Zhao, Hailing Chen, Zhengbiao Zhang, Wei Zhang, Xiulin Zhu

Reactive and Functional Polymers 2017 Volume 121(Volume 121) pp:

Publication Date(Web):1 December 2017

DOI:10.1016/j.reactfunctpolym.2017.10.014

A novel circular dichroism (CD)-silent π-conjugated polyfluorene bearing the bulky crown ether pendant (PF8C4) as the potassium ion binding site was successfully prepared by polymerization of the corresponding monomers with palladium catalyst. The polymer containing polar groups was found to form the eximious helical assembly by aggregating in chiral limonene at a lower temperature. The aggregates obtained from R- and S-limonene exhibited mirror-image CD peaks in the UV–vis region of polymer backbone. Therefore, the chirality of enantiopure limonene was successfully transferred to the optically inactive PF8C4, and the relative P- and M-helical supramolecules were successfully prepared. Moreover, after appending K+ ion to the helical supramolecules, the complexation between the K+ ion and the crown ether pendant helped to strengthen the optical activity, and thus more stable optically active supramolecular structures were achieved.We used Suzuki coupling polymerization to synthesize homo- and copolyfluorenes bearing crown ether pendant. Because of the presence of strong polar group, the copolyfluorene could assemble in chiral limonene quickly, and the corresponding P- and M-helical supramolecules were successfully prepared. After appending K+ ion to the helical supramolecules, the optical activity was further enhanced by the complexation between the K+ ion and crown ether pendant.Download high-res image (194KB)Download full-size image

Induction of supramolecular chirality by chiral solvation in achiral Azo polymers with different spacer lengths and push–pull electronic substituents: where will chiral induction appear?

Co-reporter:Lu Yin;Yin Zhao;Meng Liu;Nianchen Zhou;Xiulin Zhu

Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 12) pp:1906-1913

Publication Date(Web):2017/03/21

DOI:10.1039/C7PY00130D

Induction of supramolecular chirality from achiral compounds has been exploited in small molecules, oligomers and polymer systems. However, the relationship between the structure of building blocks and induction of supramolecular chirality is often poorly understood. Herein, we designed and synthesized a series of azobenzene (Azo) side-chain polymers with different spacer lengths (n is the number of methylene units in the spacer, n = 0, 2, 4, 6, 11) and push–pull electronic substituents (R is the terminal group of the Azo unit, R = OCH3, CH3, CN, N(CH3)2, H) by reversible addition–fragmentation chain transfer polymerization. The structure of achiral side-chain Azo polymers with different push–pull groups and spacer lengths had strong effects on supramolecular chirality induced by chiral limonene. No apparent chiral amplification phenomena were observed for all Azo polymer systems. These aggregates of several Azo polymers in dichloroethane/limonene mixed solvent were characterized by circular dichroism (CD) and UV-vis spectroscopy, demonstrating the successful chirality transfer from limonene molecules to PM4Az, PM6Az, PM11Az, PM6CN and PM6N. However, when spacer lengths were shorter (PM0Az and PM2Az), the supramolecular chirality arising from well-assembled achiral side-chain Azo units was not observed and the polymer aggregates had no CD signal. Meanwhile, the CD signal was absent for Azo polymers containing CH3 or H terminal groups. The polymers with longer spacer lengths (PM11Az) showed better reversibility of the chiral–achiral switch by trans–cis photoisomerization and cis–trans thermal-isomerization processes compared to PM4Az, PM6Az and PM6CN. Intriguingly, the chiral aggregate of PM6N showed good stability of supramolecular chirality under 405 nm light exposure over 40 min. These findings will not only provide significant insight into the structure–property relationship for inducing supramolecular chirality from achiral polymers, but also give cues for design of stabilized chiroptical materials.

Synthesis of diverse cyclic-brush polymers with cyclic polystyrene as a universal template via a grafting-from approach

Co-reporter:Shuangshuang Zhang, Lu Yin, Wei Zhang, Zhengbiao Zhang and Xiulin Zhu

Polymer Chemistry 2016 vol. 7(Issue 11) pp:2112-2120

Publication Date(Web):12 Feb 2016

DOI:10.1039/C6PY00012F

Combining the ring-closure method with the “grafting from” method, a novel synthetic strategy for preparing cyclic-brush polymers with controlled grafting density was successfully demonstrated. The cyclic polystyrene (c-PS) precursor was synthesized using the general methods of activators generated by electron transfer for atom transfer radical polymerization (AGET-ATRP) and Cu-catalyzed azide–alkyne cycloaddition (CuAAC), and was well characterized using NMR, GPC, MALDI-TOF mass spectroscopy and FT-IR. The benzylic hydrogen atoms of c-PS were substituted with bromine based on Wohl–Ziegler bromination to generate a tertiary bromide ATRP macroinitiator (c-PSBr), and the bromine content can be adjusted to 18.4%, 25.3%, 31.9% and 50.3% by using different reaction conditions. This ATRP macroinitiator can also be converted into a macro-RAFT agent with azole (c-PSN) or ethyoxyl (c-PSO) as the Z groups based on the styrenic polymers as the R group. Using the as-prepared ATRP macroinitiator or macro-RAFT agents, a series of cyclic-brush polymers including c-PS-g-PS, c-PS-g-PNIPAM, c-PS-g-PMMA, c-PS-g-PMA and c-PS-g-PVAc were successfully prepared. The grafting density can be facilely tuned by using variable Br content of c-PSBr or Z group content of the macro-RAFT agents. The work illustrated a first example of versatile synthesis of cyclic-brush polymers with predictable molecular weight, grafting density and different grafting polymer chains.

Synthesis and characterization of visible-light-activated Azo hyperbranched polymers

Co-reporter:Laibing Wang, Yang Chen, Lu Yin, Shuangshuang Zhang, Nianchen Zhou, Wei Zhang and Xiulin Zhu

Polymer Chemistry 2016 vol. 7(Issue 34) pp:5407-5413

Publication Date(Web):02 Aug 2016

DOI:10.1039/C6PY01232A

All visible-light-activated Azo photoswitches have recently blossomed. Herein two kinds of photoresponsive Azo hyperbranched polymers, HPTOF and HPTNF, were efficiently synthesized from the respective trinitro-functionalized monomers via combination of the AuNP-catalyzed photocatalytic method and the A3 monomer strategy. The polymerization process showed a very high monomer conversion (>95%) and a perfect selectivity. The molecular weights of the obtained Azo hyperbranched polymers were much higher than those of linear systems as reported previously, which could be efficiently adjusted by controlling the dosages of the mononitro-compound (the end-capping reagent) employed in the polymerization system. The resulting Azo hyperbranched polymers were well characterized by using GPC, NMR, FT-IR and UV-vis spectra. From unusual to common Azo-polymers, the π–π* absorptions in the UV-vis spectra show significant red-shifts; therefore the photoisomerizations of these Azo-polymers (HPTOF and HPTNF) can be induced by visible light. Interestingly, HPTOF and HPTNF demonstrated a double-wavelength (532 nm green light and 313 nm UV light) light-responsive Z → E photoisomerization. The relatively lower photoswitching ability of HPTNF than that of HPTOF was attributed to the partial overlap of π–π* (Z-isomer) and n–π* (E-isomer) transitions resulting from its much longer extending π-conjugation structure.

Supramolecular Chirality in Achiral Polyfluorene: Chiral Gelation, Memory of Chirality, and Chiral Sensing Property

Co-reporter:Yin Zhao, Nor Azura Abdul Rahim, Yijun Xia, Michiya Fujiki, Bo Song, Zhengbiao Zhang, Wei Zhang, and Xiulin Zhu

Macromolecules 2016 Volume 49(Issue 9) pp:3214-3221

Publication Date(Web):April 21, 2016

DOI:10.1021/acs.macromol.6b00376

Producing supramolecular chirality from achiral π-conjugated polymers toward preferred chiral memory, effective circularly polarized luminescence, and chiral sensor is extremely important in design of functional chiral materials. Proposed herein is an effective protocol to generate and memorize the supramolecular chirality formed from achiral poly(9,9-dioctylfluorene) (PF8) induced by chiral solvation. The process of chiral supramolecular assembly was monitored by UV–vis spectroscopy, circular dichroism (CD), and fluorescent spectroscopy. Achiral PF8 dissolved in neat (R)-(+)-limonene (1R) and (S)-(−)-limonene (1S) underwent chiral sol–gel transition at −20 °C. PF8 aggregates revealed intense CD and circularly polarized luminescence (CPL) signals due to β-phase, exhibiting absolute dissymmetry ratio of ≈2 × 10–3 at 430–470 nm. The supramolecular chirality of PF8 aggregates can be perfectly memorized in solid film even near decomposition temperature (300 °C), comparing favorably with that from chiral polyfluorene. Atomic force microscopy (AFM) inferred helically distorted PF8 aggregate motifs responsible for the CD and CPL functionality. Furthermore, the first chiral sensor to detect nonracemic limonene molecules employing achiral PF8 spin-cast film from CHCl3 solution was achieved.

Photon magic: chiroptical polarisation, depolarisation, inversion, retention and switching of non-photochromic light-emitting polymers in optofluidic medium

Co-reporter:Michiya Fujiki, Yuri Donguri, Yin Zhao, Ayako Nakao, Nozomu Suzuki, Kana Yoshida and Wei Zhang

Polymer Chemistry 2015 vol. 6(Issue 9) pp:1627-1638

Publication Date(Web):08 Dec 2014

DOI:10.1039/C4PY01337A

Circularly polarised (CP)-photons at six different energies (six wavelengths) were irradiated to non-photochromic, highly photoluminescent poly[(9,9-di-n-octylfluoren-2,7-diyl)-alt-bithiophene] (PF8T2) as μm-sized particles in chloroform–methanol cosolvents. This approach led to the capability of photophysically controlling all chiroptical polarisation, depolarisation, inversion, retention and switching in the ground and/or photoexcited states, as proven by circular dichroism (CD), optical rotation dispersion (ORD) and circularly polarised luminescence (CPL) spectroscopy. By optofluidically tuning the refractive index of the cosolvents at 589 nm (nD), these CP-photon induced CD signals were resonantly enhanced at a specific nD of ≈1.40. Surprisingly, regardless of the same l- (and r-) CP hand, the choice of higher and lower CP-photon energies led to a swapping of signs in chiroptical polarisation of the particles. The CP-photon hand, l- and r-, was not a deterministic factor for the induced chiroptical sign of the PF8T2 particles. This anomaly originates from CD inversion characteristics between lower and higher energy regions, supported by ZINDO calculations of PF8T2 model oligomers. Finally, controlled CP-photon sense and irradiating energy successfully allowed CPL-silent PF8T2 particles (quantum yield of 15%) to change to CPL-active particles of the order of |gCPL| = (1.9–4.3) × 10−3 at ≈535 nm whilst almost keeping the quantum yield of 8%.

Photocontrollable induction of supramolecular chirality in achiral side chain Azo-containing polymers through preferential chiral solvation

Co-reporter:Shunqin Jiang, Yin Zhao, Laibing Wang, Lu Yin, Zhengbiao Zhang, Jian Zhu, Wei Zhang and Xiulin Zhu

Polymer Chemistry 2015 vol. 6(Issue 23) pp:4230-4239

Publication Date(Web):23 Apr 2015

DOI:10.1039/C5PY00496A

Here we designed a trans–cis photoisomerizable achiral side chain azobenzene-containing polymer, poly(6-[4-(4-methoxyphenylazo) phenoxy] hexyl methacrylate) (PAzoMA), to investigate the possibility of transferring chirality of chiral solvent molecules to polymers. Preferred chirality in supramolecularly assembled trans-azobenzene units of PAzoMA is successfully induced by limonene chirality. This chiral solvation induced chirality arises from superstructural chirality of well-assembled achiral azobenzene units in polymer side chains. The intense bisignated circular dichroism (CD) signals in the UV-vis region disappeared when trans–cis photoisomerization of PAzoMA occurred with 365 nm light irradiation. The polymer aggregate solution shows the CD-silent state when the cis-PAzoMA solution is subjected to 436 nm light irradiation. The intense CD signals with a ∼40 nm red-shift were recovered by heating the polymer aggregate solution to 60 °C and keeping it at this temperature for 40 min, then cooling it down to room temperature. The successful construction of a reversible chiral–achiral switch based on an achiral azobenzene-containing side chain polymer will open a new approach for production of chiroptical materials.

The Suzuki coupling reaction as a post-polymerization modification: a promising protocol for construction of cyclic-brush and more complex polymers

Co-reporter:Yunshu Wang, Shuangshuang Zhang, Laibing Wang, Wei Zhang, Nianchen Zhou, Zhengbiao Zhang and Xiulin Zhu

Polymer Chemistry 2015 vol. 6(Issue 25) pp:4669-4677

Publication Date(Web):12 May 2015

DOI:10.1039/C5PY00551E

Cyclic poly(4-bromostyrene) (c-PBrS), synthesized via a combination of atom transfer radical polymerization (ATRP) and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), was employed as a universal cyclic precursor to prepare cyclic-brush polymers by the Suzuki coupling reaction. Cyclic functional poly[(4-methoxyphenyl)styrene] and cyclic-brush polystyrene have been achieved by the Suzuki coupling reaction as a post-modification, endowing excellent modification efficiency (∼100%), i.e., all the repeating units have been completely transformed into target ones. The obtained polymer structures were carefully characterized by NMR, GPC and MALDI-TOF mass spectra. This study undoubtedly offers a highly efficient and promising post-modification protocol to prepare cyclic-brush polymers or other more complex ones, the preparation of which was previously highly challenging.

Preferential chiral solvation induced supramolecular chirality in optically inactive star Azo polymers: photocontrollability, chiral amplification and topological effects

Co-reporter:Lu Yin, Yin Zhao, Shunqin Jiang, Laibing Wang, Zhengbiao Zhang, Jian Zhu, Wei Zhang and Xiulin Zhu

Polymer Chemistry 2015 vol. 6(Issue 39) pp:7045-7052

Publication Date(Web):20 Aug 2015

DOI:10.1039/C5PY01175B

A series of star-shaped azobenzene (Azo)-containing side chain polymers with 3, 4 and 6 arms were synthesized by the atom transfer radical polymerization technique initiated by multifunctional initiators. The intense bisignated circular dichroism (CD) signals in the UV–vis region were observed when these star polymers aggregated in a dichloroethane/limonene mixed solvent, indicating the successful chirality transfer from limonene molecules to these star Azo polymers. The chirality originates from the preferential supramolecular chirality of well-organized optically inactive side-chain Azo units. The supramolecular chirality is closely related to the volume fraction of cosolvents, the enantiopurity (ee) of limonene, molecular weight and arm numbers of star Azo polymers. Interestingly, the maximum values of CD and gCD of the polymer aggregates increase with molecular weight in the case of 3-armed Azo polymers, and increase simultaneously with arm numbers of the polymers having similar repeating units under each optimized experimental condition. Surprisingly, the first chiral amplification behaviours were observed in the 4- and 6-armed Azo polymers, but absent in linear and 3-armed counterparts. The supramolecular chirality can be destroyed by trans–cis photoisomerization and recovered by thermal cis–trans isomerization of Azo units. The current research will provide further insight into the mechanism study and production of effective chiroptical materials in chiral solvation induced supramolecular chirality of the achiral polymers.

A Straightforward Protocol for the Highly Efficient Preparation of Main-Chain Azo Polymers Directly from Bisnitroaromatic Compounds by the Photocatalytic Process

Co-reporter:Laibing Wang, Xiangqiang Pan, Yin Zhao, Yang Chen, Wei Zhang, Yingfeng Tu, Zhengbiao Zhang, Jian Zhu, Nianchen Zhou, and Xiulin Zhu

Macromolecules 2015 Volume 48(Issue 5) pp:1289-1295

Publication Date(Web):February 19, 2015

DOI:10.1021/acs.macromol.5b00048

A novel strategy for the synthesis of main-chain Azo polymers directly from bisnitroaromatic compounds by the photocatalytic process has been achieved under mild conditions. This approach avoids the tedious synthesis of Azo monomers and proceeds with a high monomer conversion (∼100%) and excellent selectivity (∼100%) but without generating a significant amount of inorganic wastes and impurities (Cu2+ or azoxy groups) existing in main-chain Azo polymers compared to previous methods. The polymerization was monitored by UV–vis, FT-IR, and MALDI-TOF-MS, indicating that the reaction process proceeded with formation of the azoxy repeating units from the corresponding bisnitroaromatic monomers and the reduction of corresponding azoxy repeating units to the azo repeating units. Furthermore, the recyclable heterogeneous photocatalysts represent an attractive green process for production of main-chain Azo polymers.

Chiroptical generation and amplification of hyperbranched π-conjugated polymers in aggregation states driven by limonene chirality

Co-reporter:Jiangfei Liu, Jian Zhang, Shuangshuang Zhang, Nozomu Suzuki, Michiya Fujiki, Laibing Wang, Liang Li, Wei Zhang, Nianchen Zhou and Xiulin Zhu

Polymer Chemistry 2014 vol. 5(Issue 3) pp:784-791

Publication Date(Web):10 Sep 2013

DOI:10.1039/C3PY01037F

In this contribution, a series of hyperbranched π-conjugated poly(9,9-di-n-octylfluorene)s (HPF8s) with hexaoctyltruxene (HT) as branching units were successfully prepared by a Suzuki polycondensation reaction. We present the first generation of optically active HPF8s in aggregation states with strong circular dichroism (CD) and circularly polarised luminescence (CPL) properties. The optically active aggregates of HPF8s were efficiently produced by CD-/CPL-silent HPF8s with the help of solvent chirality transfer from chiral limonene at room temperature. The emergence of CD and CPL signals of HPF8s aggregates results from the weak forces (π/π, van der Waals, CH/π and OH/π interactions) in a tersolvent system of chloroform (a good solvent), alkanol (a poor solvent), and (R)-(+)-/(S)-(−)-limonene (1R/1S, a chiral source). The hyperbranched polymer structure (degree of branching), poor solvent type, volume fraction of methanol and 1R/1S, limonene enantiopurity and polymer concentration have obvious effects on the magnitude and sign of the CD signals. The obtained HPF8s aggregates have relatively strong UV-vis absorption and CD signals in the range of 300–500 nm as well as CPL emission (420–460 nm) under optimised conditions. The current study will open up a new avenue for efficiently producing ambidextrous chiroptical hyperbranched polymeric materials without any specific chiral catalysts or substituents under mild conditions.

A novel approach to synthesize polymers for potential photodynamic therapy: from benzenedinitrile to phthalocyanine

Co-reporter:Laibing Wang, Jun Li, Weidong Zhang, Gaojian Chen, Wei Zhang and Xiulin Zhu

Polymer Chemistry 2014 vol. 5(Issue 8) pp:2872-2879

Publication Date(Web):08 Jan 2014

DOI:10.1039/C3PY01129A

Benzenedinitrile, a precursor for the synthesis of phthalocyanine, was incorporated into a methacrylate monomer, 2-methyl-acrylic acid 6-(3,4-dicyano-phenoxy)-hexyl ester (MADCE). The benzenedinitrile monomer was homo-polymerized, chain-extended and copolymerized with oligo(ethylene glycol) methyl methacrylate (OEGMEMA) via the reversible addition–fragmentation chain transfer (RAFT) method. The resulting homopolymer, block and random copolymers obtained were used to synthesize polymers with Zn(II)phthalocyanine (ZnPc) side-chains by reacting with excess benzenedinitrile derivatives, 4-(octyloxy)phthalonitrile (OPN). GPC, FTIR, UV-Vis, NMR, fluorescence, and atomic absorption spectroscopy were used to characterize the Zn(II)phthalocyanine-functionalized polymers. The ZnPc-functionalized polymers generate singlet oxygen species with good quantum yields, which are believed to be the major cytotoxic reactive oxygen species (ROS) for photodynamic therapy. Among them, copolymers present enhanced singlet oxygen quantum yields (ΦΔ = 0.49 and 0.40 in DMF, ΦΔ = 0.68 and 0.73 in aqueous media) compared to the homopolymer (ΦΔ = 0.28). The ZnPc-functionalized copolymers self-assembled into nanoparticles in aqueous solutions, which was confirmed by DLS and TEM, and the nanoparticles show good stability in the presence of salt and proteins. This novel and efficient method of synthesizing water-soluble ZnPc-functionalized polymers with good singlet oxygen quantum yields provides a simple approach to fabricate polymeric materials for photodynamic therapy.

Limonene induced chiroptical generation and inversion during aggregation of achiral polyfluorene analogs: structure-dependence and mechanism

Co-reporter:Laibing Wang, Nozomu Suzuki, Jiangfei Liu, Takashi Matsuda, Nor Azura Abdul Rahim, Wei Zhang, Michiya Fujiki, Zhengbiao Zhang, Nianchen Zhou and Xiulin Zhu

Polymer Chemistry 2014 vol. 5(Issue 20) pp:5920-5927

Publication Date(Web):31 Jul 2014

DOI:10.1039/C4PY00865K

Chirality transfer from biological agents to π-conjugated polymers in the solid state is an attractive method to generate, switch, and amplify chirality, especially when one considers several potent device applications. However, the polymer-structure dependence on the solvent-induced chirality transfer mechanism is not well understood. To elucidate the structural–chiroptical property relationship of the polymer aggregates, poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PF8), poly(9,9-di-n-octylsila-fluorenyl-2,7-diyl) (PSi8), poly(9-(1-octylnonyl)-9H-carbazole-2,7-diyl) (PCz8), P(F8-alt-Si8), P(F8-alt-Cz8), and P(Si8-alt-Cz8) were synthesized. The limonene chirality was efficiently transferred to PF8, PSi8 and P(F8-alt-PSi8) aggregates in CHCl3–limonene–CH3OH tersolvent, but the optical activity was not observable for PCz8, P(F8-alt-PCz8), and P(Si8-alt-PCz8). The reason for the absence of chiroptical activity in Cz8-containing polymers could be that those polymers have stronger polarity compared to limonenes, and thus the interaction between limonene and polymer chains was too weak compared to the interaction among Cz8-containing polymers. Surprisingly, chiroptical inversion in CD spectra between PF8 and PSi8 aggregates was found. More surprisingly, chiroptical inversion between CD and CPL spectra of PSi8 aggregates was observed. The unique chiroptical inversion was attributable to the opposite Mulliken charges between 9-Si in Si8 and 9-C in F8 unit and between Cipso(1) in Si8 and Cipso(1) in F8 unit. Another possible reason for this unexpected chiroptical inversion behaviour is the opposite direction of dipole moments in three stable rotational isomers of the equatorial limonene rotamer.

A novel azobenzene covalent organic framework

Co-reporter:Jian Zhang, Laibing Wang, Na Li, Jiangfei Liu, Wei Zhang, Zhengbiao Zhang, Nianchen Zhou and Xiulin Zhu

CrystEngComm 2014 vol. 16(Issue 29) pp:6547-6551

Publication Date(Web):27 May 2014

DOI:10.1039/C4CE00369A

A novel azobenzene (Azo) monomer was synthesized and employed to produce Azo-containing covalent organic frameworks (Azo-COF) through the borate ester formation reaction. The trans-to-cis photoisomerization of Azo units in Azo-COF occurred under irradiation with 365 nm UV light. The photoisomerization of Azo units could decrease the crystallinity of Azo-COF but could not change the pore size of Azo-COF.

Supramolecular self-assembly and photovoltaic property of soluble fluorogallium phthalocyanine

Co-reporter:Jian Zhang, Yaowen Li, Laibing Wang, Michiya Fujiki, Xiaopeng Li, Zhengbiao Zhang, Wei Zhang, Nianchen Zhou and Xiulin Zhu

RSC Advances 2014 vol. 4(Issue 56) pp:29485-29492

Publication Date(Web):13 Jun 2014

DOI:10.1039/C4RA03941F

Within the present work, two soluble phthalocyanine compounds, fluorogallium tetra-tert-butylphthalocyanine (ttbPcGaF) and its precursor hydroxygallium tetra-tert-butylphthalocyanine (ttbPcGaOH) were successfully synthesized. ttbPcGaF had a considerably stronger ability than that of ttbPcGaOH to self-organize into well-ordered one-dimensional (1D) supramolecular polymers in solid state by solution-coating technique. The photovoltaic properties of ttbPcGaF and ttbPcGaOH as electron donor materials in solution-processed bulk heterojunction (BHJ) organic solar cells (OSCs) were investigated. Due to the retention of the self-assembly property of ttbPcGaF and nanoscale phase separation in the ttbPcGaF:PC61BM blend film, the ttbPcGaF-based BHJ OSC provided a profoundly improved power conversion efficiency (PCE) of 0.41%, as compared with a low PCE of 0.03% afforded by ttbPcGaOH.

Preparation and characterization of solution processable phthalocyanine-containing polymers via a combination of RAFT polymerization and post-polymerization modification techniques

Co-reporter:Jian Zhang;Laibing Wang;Chao Li;Yaowen Li;Jiangfei Liu;Yingfeng Tu;Nianchen Zhou ;Xiulin Zhu

Journal of Polymer Science Part A: Polymer Chemistry 2014 Volume 52( Issue 5) pp:691-698

Publication Date(Web):

DOI:10.1002/pola.27051

ABSTRACT

In this work, a benzenedinitrile functionalized monomer, 2-methyl-acrylic acid 6-(3,4-dicyano-phenoxy)-hexyl ester, was successfully polymerized via the reversible addition-fragmentation chain transfer method. The polymerization behavior conveyed the characteristics of “living”/controlled radical polymerization: the first-order kinetics, linear increase of number-average molecular weight with monomer conversion, narrow molecular weight distribution, and successful chain-extension experiment. The soluble Zn(II) phthalocyanine (Pc)-containing (ZnPc) polymers were achieved by post-polymerization modification of the obtained polymers. The Zn(II) phthalocyanine-functionalized polymer was characterized by FTIR, UV–vis, fluorescence, atomic absorption spectroscopy, and thermogravimetric analysis. The potential application of above ZnPc-functionalized polymer as electron donor material in bulk heterojunction organic solar cell was studied. The device with ITO/PEDOT:PSS/ZnPc-Polymer/PC₆₁BM/LiF/Al structure provided a power conversion efficiency of 0.014%, fill factor of 0.24, open circuit voltage (V_oc) of 0.21 V, and short-circuit current (J_sc) of 0.28 mA/cm². © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 691–698

Cooperative self-assembly and crystallization into fractal patterns by PNIPAM-based nonlinear multihydrophilic block copolymers under alkaline conditions

Co-reporter:Shengtong Sun, Shengjie Xu, Weidong Zhang, Peiyi Wu, Wei Zhang and Xiulin Zhu

Polymer Chemistry 2013 vol. 4(Issue 24) pp:5800-5809

Publication Date(Web):19 Jul 2013

DOI:10.1039/C3PY00682D

Hierarchical two-dimensional patterned nanomaterials fabricated by bottom-up self-assembly are of great interests in practical applications. A series of nonlinear multihydrophilic block copolymers (MHBCs), consisting of poly(N-isopropylacrylamide) (PNIPAM), poly(acrylic acid) (PAA) and/or poly(vinyl pyrrolidone) (PVP) segments, were employed to fabricate well-defined fractal patterns under alkaline conditions by a simple solvent evaporation process. The formation of fractal patterns was discovered to obey a diffusion-limited aggregation process by needle-shaped intermediate nanostructures, which are actually nanohybrids formed by the cooperative self-assembly and crystallization of polymers and alkalis. The ability of MHBCs to form fractal patterns is closely related to their structural architectures, and is also significantly influenced by temperature, alkaline concentration, alkali type and substrate. Upon evaporation, PAA segments serve as the growing scaffolds of alkali crystallization along with the occurrence of self-contraction and intermolecular association of PNIPAM segments. PVP segments are not necessary for fractal patterning, which, however, can prompt the self-assembly into more perfect dendritic patterns in the case of a proper structural linking sequence. The observations reported here can provide a better understanding of molecular self-assembly toward complex patterns at multiple length scales, which may gain potential applications in advanced devices, sensors and microprinting.

Effect of structural constraint on dynamic self-assembly behavior of PNIPAM-based nonlinear multihydrophilic block copolymers

Co-reporter:Shengtong Sun, Peiyi Wu, Weidong Zhang, Wei Zhang and Xiulin Zhu

Soft Matter 2013 vol. 9(Issue 6) pp:1807-1816

Publication Date(Web):12 Dec 2012

DOI:10.1039/C2SM27183D

The effects of structural constraint on the thermosensitivity and dynamic self-assembly behaviors of PNIPAM-based nonlinear multihydrophilic block copolymers (MHBCs) are investigated by a combination of calorimetric, NMR, FTIR, DLS and zeta potential measurements. Two novel miktoarm star MHBCs, (PNIPAM)2-(PVP-b-PAA)2 with PNIPAM segments constrained at one end and (PNIPAM-b-PAA)2-(PVP)2 with PNIPAM segments constrained at two ends, are mainly analyzed to make comparison. As we previously reported (Soft Matter, 2012, 8, 3980), in (PNIPAM)2-(PVP-b-PAA)2 the three polymeric segments have relatively independent phase behaviors during the formation of PNIPAM-core micelles. However, by introducing more structural constraints to PNIPAM segments, (PNIPAM-b-PAA)2-(PVP)2 exhibits a much smoother and weaker phase transition. Additional analysis by IR spectroscopy, in combination with perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2DCOS), indicates that PVP segments in (PNIPAM-b-PAA)2-(PVP)2 show phase transition-like behavior by participating in the self-association process of PNIPAM segments, and there are both unimers and small associates existing in the solution below the LCST due to the slight interaction between PVP and PNIPAM segments. Moreover, due to the presence of PVP segments in the core, the micelles formed by (PNIPAM-b-PAA)2-(PVP)2 should have a loosely organized superstructure, which may account for the weak phase transition and low degree of phase separation. Finally, we propose a mechanism of the self-assembly process of (PNIPAM-b-PAA)2-(PVP)2, which is further confirmed by DLS and zeta potential measurements.

Design and property of thermoresponsive coreshell fluorescent nanoparticles via RAFT polymerization and suzuki coupling reaction

Co-reporter:Zeyong Xing;Jian Zhang;Xiaohong Li, ;Laibing Wang;Nianchen Zhou ;Xiulin Zhu

Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 19) pp:4021-4030

Publication Date(Web):

DOI:10.1002/pola.26822

ABSTRACT

The polymerization of a 2,7-dibromocarbazole-containing functional monomer, 6-(2,7-dibromo-9H-carbazol-9-yl)hexyl methacrylate (DBCzMA), was successfully carried out via the reversible addition-fragmentation chain transfer (RAFT) technology. The polymerization behavior possessed the feature of “living”/controlled radical polymerization, for example, the first-order kinetics, the linear increase of the molecular weight of the polymer with the monomer conversion and relatively narrow molecular weight distribution (M_w/M_n ≤ 1.27). The amphiphilic copolymers, poly(DBCzMA_m-b-NIPAM_n), with different chain length of poly(DBCzMA) and poly(N-isopropylacrylamide) (PNIPAM), were successfully prepared via RAFT chain-extension reaction, using poly(DBCzMA) as the macromolecular chain transfer agent (macro-CTA) and NIPAM as the second monomer. Modification of 2,7-dibromide groups in amphiphilic copolymer poly(DBCzMA-b-NIPAM) via Suzuki coupling reaction employed 2,7-bis(4′,4′,5′,5′-tetramethyl-1′,3′,2′-dioxaborolan-2′-yl)-N−9″-heptadecanylcarbazole as the other reaction material to afford a poly(2,7-carbazole)-containing crosslinked materials. The stable and uniform core–shell fluorescent nanoparticles were successfully prepared in water. The formed fluorescent nanoparticles showed good thermoresponsive properties, which is confirmed by dynamic light scattering observation. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4021–4030

Facile one-pot/one-step technique for preparation of side-chain functionalized polymers: Combination of SET-RAFT polymerization of azide vinyl monomer and click chemistry

Co-reporter:Qiong Shen;Jian Zhang;Shuangshuang Zhang;Yigang Hao;Weidong Zhang;Gaojian Chen;Zhengbiao Zhang;Xiulin Zhu

Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 6) pp:1120-1126

Publication Date(Web):

DOI:10.1002/pola.25868

Abstract

An azido-containing functional monomer, 11-azido-undecanoyl methacrylate, was successfully polymerized via ambient temperature single electron transfer initiation and propagation through the reversible addition–fragmentation chain transfer (SET-RAFT) method. The polymerization behavior possessed the characteristics of “living”/controlled radical polymerization. The kinetic plot was first order, and the molecular weight of the polymer increased linearly with the monomer conversion while keeping the relatively narrow molecular weight distribution (M_w/M_n ≤ 1.22). The complete retention of azido group of the resulting polymer was confirmed by ¹H NMR and FTIR analysis. Retention of chain functionality was confirmed by chain extension with methyl methacrylate to yield a diblock copolymer. Furthermore, the side-chain functionalized polymer could be prepared by one-pot/one-step technique, which is combination of SET-RAFT and “click chemistry” methods. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Chiroptical Nanofibers Generated from Achiral Metallophthalocyanines Induced by Diamine Homochirality

Co-reporter: Wei Zhang; Michiya Fujiki; Xiulin Zhu

Chemistry - A European Journal 2011 Volume 17( Issue 38) pp:10628-10635

Publication Date(Web):

DOI:10.1002/chem.201100208

Abstract

Optically active cofacial π–π phthalocyanine (Pc) stacked supramolecules were spontaneously and successfully generated from a mixture of four possible geometric isomers (C_4h, D_2h, C_2v, C_s) of achiral 4(5),4′(5′),4′′(5′′),4′′′(5′′′)-tetracarboxymetallophthalocyanine (tcPcM; M=Ni, Cu) induced by an equimolar amount of inexpensive chiral diamine molecular sources in DMSO/CHCl₃ mixed solvent under optimized conditions of the volume ratio of poor/good cosolvents, the molar ratio of chiral molecular diamine to tcPcM, the cavity metal of phthalocyanine, and the addition order of the amines. The sign and amplitude of circular dichroism spectra due to the supramolecular chirality and structure of the diamine molecules are impossible to remove by additions of the antipode diamine and trifluoroacetic acid. The chiral diamine was partly contained in nanofibers, and that retained in the solution can be recycled and reused to induce optically active tcPcM supramolecules.

Unpolarized-Light-Driven Amplified Chiroptical Modulation Between Chiral Aggregation and Achiral Disaggregation of an Azobenzene-alt-Fluorene Copolymer in Limonene

Co-reporter:Wei Zhang ; Kana Yoshida ; Michiya Fujiki ;Xiulin Zhu

Macromolecules () pp:

Publication Date(Web):June 16, 2011

DOI:10.1021/ma2012128

A trans–cis photoisomerizable achiral polymer, poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-4,4′-azobenzene] (F8AZO), was designed. The chirality of (S)- and (R)-limonene used as a solvent allowed for the generation of optically active F8AZO aggregates, revealing intense circular dichroism (CD) signals in the visible region. The reversible chiroptical response was achieved upon alternating photoirradiation at 405 nm (trans-form) and 546 nm (cis-form). This ability originated from the switching between the trans-origin aggregation and cis-origin disaggregation of F8AZO in the limonene–2-propanol–chloroform tersolvent.