Co-reporter:Chenyang Xing;Yanyuan Wang;Cong Zhang;Jingye Li;Linfan Li
Industrial & Engineering Chemistry Research September 30, 2015 Volume 54(Issue 38) pp:9351-9359
Publication Date(Web):2017-2-22
DOI:10.1021/acs.iecr.5b02819
An unsaturated room-temperature ionic liquid (IL), 1-vinyl-3-butylimidazolium chloride [VBIM][Cl], has been grafted onto poly(vinylidene fluoride) (PVDF) by electron beam irradiation at room temperature. The structure and physical properties of IL grafted PVDF (PVDF-g-IL) were investigated. Both the extraction experiments and 1H NMR results indicated the successful grafting of IL onto PVDF molecular chains. It was calculated that IL grafting yield was approximately 3.9 per 100 repeating units of PVDF, suggesting very short IL grafting sequences. The melting temperatures (Tm) of the PVDF-g-IL films decreased with absorbed dose, suggesting the occurrence of crystal defects of PVDF caused by the irradiation. However, the morphologies, crystal forms and crystal long periods (L) of PVDF-g-IL films were not significantly influenced by the irradiation. Moreover, the effects of IL grafting and absorbed dose on physical properties of PVDF-g-IL films were investigated. It was found that the irradiation could immobilize IL molecules onto PVDF chains and thus suppressed their migration in electric filed. Therefore, the grafted samples showed lower dielectric loss, electrical conductivity as well as dielectric permittivity compared with the unirradiated blends. Moreover, the elongation at break of the grafted PVDF decreased with the applied irradiation dose, but the Young’s modulus increased. The as-prepared PVDF-g-IL composites exhibited large dielectric permittivity, low dielectric loss and, in particular, excellent toughness, which is promising for use in dielectric capacitor applications.
Co-reporter:Depei Chen, Hengti Wang, and Yongjin Li
ACS Applied Materials & Interfaces September 27, 2017 Volume 9(Issue 38) pp:33091-33091
Publication Date(Web):September 8, 2017
DOI:10.1021/acsami.7b08699
Reactive compatibilizers are usually used to enhance the compatibility of immiscible polymer blends. However, reactive linear compatibilizers containing reactive groups on the main chains form graft copolymers during reactive blending, and such graft copolymers with an asymmetric molecular structure are often “pulled in” or “pulled out” under mechanical shear. Double-grafted compatibilizers have a symmetric structure, and they usually exhibit higher compatibilizing efficiency. In this work, we propose a binary grafting strategy during melt blending to form compatibilizers located at the interface of an immiscible polymer blend. Specifically, poly(methyl methacrylate) (PMMA) oligomer with carboxylic end groups (PMMA–COOH) and poly(styrene-co-glycidyl methacrylate) (SG) copolymer were simultaneously incorporated into immiscible poly(vinylidene fluoride)/poly(l-lactic acid) (PVDF/PLLA) blends. The carboxylic acid groups of both the PMMA oligomer and PLLA can react with the epoxide groups on the SG main chains. Therefore, novel compatibilizing polymers with both PMMA and PLLA chains grafted onto the SG main chains form in situ. The grafted PMMA chains can entangle with PVDF, and the grafted PLLA chains are embedded in the PLLA phase, so the double-grafted copolymers act as effective compatibilizers for the PVDF/PLLA blends. Moreover, the effects of the PMMA molecular weight and PMMA loading (number of grafted PMMA side chains) on the compatibilization efficiency were investigated. The compatibilizing efficiency increases with increasing molecular weight and number of side chains in the ranges considered in this study. This one-pot synthesis of double-grafted compatibilizers by in situ grafting provides a new and simple method to prepare double-comb compatibilizers, and it offers the possibility of high-efficiency compatibilization.Keywords: compatibilization; immiscible polymer blends; interface; morphology; reactive blending;
Co-reporter:Lijun Ye;Jipeng Guan;Zhixiang Li;Jingxin Zhao;Cuicui Ye;Jichun You
Langmuir February 14, 2017 Volume 33(Issue 6) pp:1368-1374
Publication Date(Web):January 4, 2017
DOI:10.1021/acs.langmuir.6b03848
A facile and versatile strategy for fabricating superhydrophobic surfaces with controllable electrical conductivity and water adhesion is reported. “Vine-on-fence”-structured and cerebral cortex-like superhydrophobic surfaces are constructed by filtering a suspension of multiwalled carbon nanotubes (MWCNTs), using polyoxymethylene nonwovens as the filter paper. The nonwovens with micro- and nanoporous two-tier structures act as the skeleton, introducing a microscale structure. The MWCNTs act as nanoscale structures, creating hierarchical surface roughness. The surface topography and the electrical conductivity of the superhydrophobic surfaces are controlled by varying the MWCNT loading. The vine-on-fence-structured surfaces exhibit “sticky” superhydrophobicity with high water adhesion. The cerebral cortex-like surfaces exhibit self-cleaning properties with low water adhesion. The as-prepared superhydrophobic surfaces are chemically resistant to acidic and alkaline environments of pH 2–12. They therefore have potential in applications such as droplet-based microreactors and thin-film microextraction. These findings aid our understanding of the role that surface topography plays in the design and fabrication of superhydrophobic surfaces with different water-adhesion properties.
Co-reporter:Jingxin Zhao, Qiucheng Yang, Tao Wang, Lian Wang, Jichun You, and Yongjin Li
ACS Applied Materials & Interfaces December 20, 2017 Volume 9(Issue 50) pp:43415-43415
Publication Date(Web):November 30, 2017
DOI:10.1021/acsami.7b16648
An effective strategy to tailor the microporous structures has been developed based on the shape memory effect in porous poly(l-lactic acid) membranes in which tiny crystals and amorphous matrix play the roles of shape-fixed phase and reversible-phase, respectively. Our results indicate that not only PLLA membranes but micropores exhibit shape memory properties. The proportional deformations on two scales have been achieved by uniaxial or biaxial tension, providing a facile way to manipulate continuously the size and the orientation degree of pores on microscale. The enhanced separation performance has been validated by taking polystyrene colloids with varying diameters as an example.Keywords: deformation; pore size; porous membranes; separation; shape memory effect;
Co-reporter:Hengti Wang, Xin Yang, Zhiang Fu, Xuewen Zhao, Yongjin Li, and Jingye Li
Macromolecules December 12, 2017 Volume 50(Issue 23) pp:9494-9494
Publication Date(Web):November 29, 2017
DOI:10.1021/acs.macromol.7b02143
Exclusive localization of nanofillers at the interface of immiscible polymer blend has been confirmed to be effective in improving compatibility and facilitating the formation of nanofiller-network with very low percolation threshold, while the rheology of such nanofiller compatibilized blends has seldom been investigated. Herein, we present a systematic rheological study on nanosilica-compatibilized PVDF/PLLA (poly(vinylidene fluoride)/poly(l-lactide)) blends. The linear viscoelastic properties of the systems are evaluated using small amplitude oscillatory shear (SAOS). It is found that the interfacial jammed Janus grafted silica (JGS) located at the interface increases dynamic moduli at low frequency even with very low filler loadings. The nonterminal effects become more pronounced with increasing JGS loadings. Weighted relaxation spectra inferred from SAOS reveals that the shape relaxation of PVDF-droplets is strongly influenced by addition of JGS. The solid-like behavior of JGS-filled blends has been attributed to both the orderly arrangement of JGS at PVDF–PLLA interface and the molecular entanglement between the grafted long tails of JGS with the molecular chains of the component polymers. In other words, JGS at the interface not only promotes strong interfacial interactions between phases, but also stimulates the formation of unique nanoparticle–polymer hybrid network, termed as “heterogeneous network” with the silica as the junctions.
Co-reporter:Jipeng Guan, Yanyuan Wang, Shilu Wu, Yongjin Li, and Jingye Li
Biomacromolecules December 11, 2017 Volume 18(Issue 12) pp:4364-4364
Publication Date(Web):November 7, 2017
DOI:10.1021/acs.biomac.7b01416
Here, we fabricated the ionic liquid (IL) grafted poly(vinylidene fluoride) (PVDF) (PVDF-g-IL) via electron-beam irradiation to fight common bacteria and multidrug-resistant “superbugs”. Two types of ILs, 1-vinyl-3-butylimmidazolium chloride (IL (Cl)) and 1-vinyl-3-ethylimidazolium tetrafluoroborate (IL (BF4)), were used. It was found that the PVDF-g-IL exhibited superior antibacterial performance, with almost the same mechanical and thermal performance as unmodified PVDF. Nonwovens and films made from PVDF-g-IL materials exhibited broad-spectrum antimicrobial activity against common bacteria and “superbugs” with the strong electrostatic interactions between ILs and microbial cell membranes. With extremely low IL loading (0.05 wt %), the cell reduction of PVDF-g-IL (Cl) nonwovens improved from 0.2 to 4.4 against S. aureus. Moreover, the antibacterial activity of PVDF-g-IL nonwovens was permanent for the covalent bonds between ILs and polymer chains. The work provides a simple strategy to immobilize ionic antibacterial agents onto polymer substrates, which may have great potential applications in healthcare and household applications.
Co-reporter:Zhiang Fu, Hengti Wang, Xuewen Zhao, Shin Horiuchi, Yongjin Li
Polymer 2017 Volume 132(Volume 132) pp:
Publication Date(Web):6 December 2017
DOI:10.1016/j.polymer.2017.11.004
•Reactive hybrid nanoparticles were synthesized and used as compatibilizers for immiscible blend.•The mixing sequence had a great influence on the in situ reactive compatibilization.•The affinity between the NP cores and the individual blend components affects the final compatibilization effects.Hybrid nanoparticles (NPs) having both reactive epoxide groups (from polyhedral oligomeric-silsesquioxane (POSS) grafts) and long poly(methyl methacrylate) (PMMA) chains, POSS(epoxy)x-g-PMMAy, were synthesized and used as reactive compatibilizers for immiscible polyvinylidene fluoride/poly(l-lactide) (PVDF/PLLA) (50/50) blends. It was anticipated that the NPs would react with the PLLA during melt mixing and would be located solely at the PLLA/PVDF interface because the PMMA side chains and the in-situ grafted PLLA chains would entangle with the PVDF and PLLA phases, respectively. However, effective compatibilization was only achieved by first blending the NPs with the PLLA followed by melt mixing with the PVDF. Elemental mapping images indicated that the NPs had a greater affinity for PVDF than for PLLA and were encapsulated in PVDF during one-step melt mixing or initial mixing with PVDF. The affinity of the compatibilizer with the blend components is therefore critically important for the effective compatibilization of immiscible polymer blends.Download high-res image (260KB)Download full-size image
Co-reporter:Yu Zhu, Qiucheng Yang, Fei Li, Huijuan Yue, Jichun You, Yongjin Li
Polymer 2017 Volume 128(Volume 128) pp:
Publication Date(Web):16 October 2017
DOI:10.1016/j.polymer.2017.09.015
•The parallel-stripe structures were fabricated in polymer blend by precise control of film thickness and resultant stability.•It is the lamellae twisting model that dominates the formation of parallel-stripe structures in PLLA/POM blend films.•The composition and isothermal crystallization temperature dependences were clarified based on the parallel stripes.Poly(l-lactic acid)/poly(oxymethylene) bulky blend is a typical system exhibiting ring-banded spherulites. In this work, however, the parallel ridges and valleys were fabricated for the first time in the blend film by the precise control of film thickness. They are named as “parallel-stripe structures” to distinguish from general “ring-banded structures”. Our results indicate that the cracks on thinner films prevent the development of ridge/valley rings along the film, accounting for the formation of these parallel structures. Consequently, they can reduce the influence of the fractal and resultant branching lamellae which makes the investigation of ring-banded structures more complicated. On the other hand, a novel in-situ etching method has been established to investigate the composition distribution of PLLA and POM in film thickness direction. As a result, the tri-layer structures including top-PLLA layer, blend layer and bottom-POM layer were reconstructed and validated by melting contact angles. Based on the atomic force microscope and transmission electron microscope results, it is concluded that the twisting model dominates the formation of parallel banded structures in PLLA/POM blend film. Furthermore, the crystallization temperature and composition dependence of lamellae twisting has been investigated in detail. On one hand, the increase of crystallization temperature leads to the well-developed POM crystal lamellae, which is the reason for the slower twisting. On the other hand, blend films with higher PLLA weight fraction produce bigger period and smaller radius during POM lamellae twisting because of the depression of the top PLLA wetting layer.Download high-res image (304KB)Download full-size image
Co-reporter:Yuanyuan Liang;Chuanxin Lin;Jipeng Guan
RSC Advances (2011-Present) 2017 vol. 7(Issue 13) pp:7460-7468
Publication Date(Web):2017/01/20
DOI:10.1039/C6RA28167B
In this study, porous polyoxymethylene/poly(L-lactide) (POM/PLLA) nanofibrous membranes (NFMs) immobilized with silver nanoparticles (Ag NPs) are obtained via the technique of electrospinning followed by the method of seed-mediated silver electroless depositing. POM/PLLA NFMs with a high surface area were functionalized with amino groups acting as anchors so that the Ag NPs with an average diameter of about 7.6 nm were well-dispersed on the fibers of POM/PLLA NFMs. The POM/PLLA NFMs with a Ag loading content of 20.7 wt% exhibit a high catalytic rate constant of 21.25 × 10−3 s−1. Furthermore, the catalytic NFMs exhibit an excellent recoverable and cyclic feature that give a more than 99% conversion of 4-nitroaniline (4-NA) after 4 reaction cycles. The continuous conversion rate of 4-NA can remain higher than 90% even after 4 hours of running time at a flow rate of 0.4 mL min−1. Therefore, the abovementioned approach based on POM/PLLA NFMs provides a useful platform for the fabrication of noble metal nanocatalysts, which could be used as the efficient catalysts in various applications.
Co-reporter:Qiucheng Yang;Yu Zhu;Jichun You
Colloid and Polymer Science 2017 Volume 295( Issue 1) pp:181-188
Publication Date(Web):2017 January
DOI:10.1007/s00396-016-3994-4
The stability of bilayer polymer films upon solvent annealing has been investigated with the help of atomic force microscopy (AFM) by taking PMMA [poly(methyl methacrylate), the upper layer] and SAN [poly(styrene-ran-acrylonitrile), the bottom layer] system as an example. Our results indicate that the stability and structure evolution depend crucially on the selectivity of the adopted annealing solvents. In the vapor of acetic acid (HAc, the selective solvent for PMMA), the upper PMMA layer dewets on the stable bottom SAN layer; upon annealing in 1, 2-dichlorobenzene (OBD, the selective solvent for SAN) vapor, the bilayer film remains stable because it is very hard for OBD molecules to penetrate and cross the upper PMMA layer. When dimethylformamide (exhibiting much higher solubility for SAN than PMMA) is used to anneal the specimen, the solvent molecules swell and cross the upper PMMA layer and enrich in the bottom SAN layer. As a result, SAN layer dewets the substrate, producing some SAN droplets while the upper PMMA is “carried” by the movement of SAN. This is the reason for the rupture of the upper film and the formation of “SAN droplets covered by PMMA islands.”
Co-reporter:Wenfeng Jiang, Yong Liu, Chunyang Yu, Shanlong Li, Yongjin Li and Yongfeng Zhou
Chemical Communications 2016 vol. 52(Issue 53) pp:8223-8226
Publication Date(Web):13 May 2016
DOI:10.1039/C6CC03445D
This study reports a new category of stimuli-responsive morphological transitions, i.e., from one morphology (e.g., vesicles) to another two different ones (e.g., nanosheets and nanofibers), by investigating the light-responsive self-assembly behaviour of a “latent double-amphiphilic” linear-hyperbranched supramolecular block copolymer.
Co-reporter:Wenyong Dong, Hengti Wang, Fanglu Ren, Junqing Zhang, Meifeng He, Tao Wu, and Yongjin Li
ACS Sustainable Chemistry & Engineering 2016 Volume 4(Issue 8) pp:4480
Publication Date(Web):June 27, 2016
DOI:10.1021/acssuschemeng.6b01420
Reactive comb (RC) polymers with different molecular architectures have been successfully synthesized by copolymerizing methyl methacrylate (MMA), glycidyl methacrylate (GMA), and a series of MMA macromer with different molecular weights. The prepared RC polymers with different lengths of side chains were applied as compatibilizers in an immiscible poly(l-lactic acid)/poly(vinylidene fluoride) (PLLA/PVDF) blend, and it was found that the RC polymers with moderate length of side chain (e.g., Mn = 4800 g mol–1) displayed better compatibilizing efficiencies than RC polymers with short side chain (e.g., Mn = 2400 g mol–1) and let alone the reactive linear (RL) polymers without side chains. The thus obtained PLLA/PVDF blends with PLLA as a matrix will provide excellent adhesion with the surfaces of the metals and cells, and it was found that RC polymers endowed the PLLA/PVDF blend with excellent toughness and the RC-compatibilized blend could be uniaxially stretched to a maximum draw ratio of 5 at room temperature (about 22 °C). FT-IR and XRD results showed that the nonpolar α phase of PVDF was completely transformed into the piezoelectric β phase (more than 95%) during the stretching.Keywords: Interface; Piezoelectric; Poly(lactic acid); Poly(vinylidene fluoride); Reactive compatibilization
Co-reporter:Wenjia Sheng, Jingxin Zhao, Zhouli Chen, Quanlin Ye, Xuxin Yang, Keke Huang, Changmin Hou, Jichun You, and Yongjin Li
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 30) pp:8292-8298
Publication Date(Web):July 20, 2016
DOI:10.1021/acs.iecr.6b01240
Novel cigarlike nanofibers with an outer-shell and inner-continuous-pore structure and resultant fabrics have been fabricated by coupling the self-assembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) containing titanium precursors with the electrospinning technique in our previous work [You et al. ACS Appl. Mater. Interfaces 2013, 5, 2278]. In the current work, the structure control in these nanofibers has been investigated in detail using scanning electron microscopy, focused ion beam, and small angle X-ray scattering. Our results indicate that electrospinning conditions, the adopted solvent, the volume fraction of PS-b-PEO block copolymer, and the amount of titanium tetraisopropoxide in the mixture produce significant effects on both outer-shell and inner-continuous structures in the nanofibers. The parameters discussed above make it possible to achieve programmable structure control in the aspect of the diameter, thickness of the outer shell, and inner continuous pore. As a result, both micropores among fibers and nanopores in certain fibers are under their control. Furthermore, the photocatalytic activity of resultant TiO2 fabrics was investigated by taking the photodegradation of Rhodamine B as an example. The results suggest that the degradation efficiency and rate constant exhibit sensitivity on the structure of nanofibers.
Co-reporter:Xin Zheng, Caixia Zhang, Chuntao Luo, Guanghua Tian, Lian Wang, and Yongjin Li
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 11) pp:2983-2991
Publication Date(Web):March 3, 2016
DOI:10.1021/acs.iecr.5b04544
The inclusion complex of thermoplastic polyurethane (TPU) and β-cyclodextrins (β-CD) with high TPU contents has been synthesized. The channel structure with large amount of uncovered TPU was confirmed by wide-angle X-ray diffraction (WAXD). High performance poly(oxymethylene) (POM) alloys were fabricated by simply melt mixing neat POM with the synthesized TPU inclusion complex (IC-TPU). The effects of the incorporation of IC-TPU on the structure and properties of POM have been investigated. Scanning electron microscope (SEM) results showed that IC-TPU was dispersed uniformly in POM matrix and there was robust interface between IC-TPU and POM matrix. Tensile test results indicated significant improvement in both strength and ductility of the IC-TPU modified POM as compared with neat POM. Moreover, the incorporation of IC-TPU resulted in the drastically enhanced thermal stability of POM. The initial degradation temperature increased as high as 40 °C with the addition of a small amount of IC-TPU. The investigation indicated that the IC-TPU exhibited a novel structure with a soft shell (uncovered TPU) and a hard core (β-CD covered TPU segments). Such “soft shell–hard core” structure improves not only the elongation at break but also the tensile strength of POM. The superior thermal stability was originated from the synergetic effects of the hydroxyl groups in β-CDs and the amino groups in TPU. The multifunctional effect of the IC-TPU opens a new avenue for the industrial application of POM.
Co-reporter:Yu Zhu, Qiucheng Yang, Jichun You and Yongjin Li
RSC Advances 2016 vol. 6(Issue 74) pp:69715-69719
Publication Date(Web):18 Jul 2016
DOI:10.1039/C6RA12723A
The critical fluctuation intensity for the occurrence of dewetting, the basic and key problem in dewetting by means of composition fluctuation, remains obscure. In this work, therefore, the stability and fluctuation intensity of polymer films upon blending a tiny amount of a miscible component was investigated by taking poly(methyl methacrylate)/poly(styrene-ran-acrylonitrile) (i.e. PMMA/SAN) as an example. Our results indicate that both neat PMMA and neat SAN films wet the substrate of silicon oxide thermodynamically. SAN (with 1% or 2% PMMA) films dewet this substrate completely, while PMMA (with tiny amount of SAN) films are stable upon annealing at 145 °C. The fit and extrapolation of the RMSroughness suggest that the composition fluctuation and consequent surface undulation intensity accounts for the difference in film stability. The higher magnitude of fluctuation intensity results in the dewetting of the SAN film. On the other hand, the stronger interaction between PMMA and silicon oxide depresses the fluctuation and surface undulation along the film, which is the reason for the stable PMMA film.
Co-reporter:Chuangjiang Ni, Yingcong Wei, Qiuxue Hu, Xiaobai Li, Baijun Liu, Qi Zhao, Mingyao Zhang, Yongjin Li, Wei Hu
Solid State Ionics 2016 Volume 297() pp:29-35
Publication Date(Web):1 December 2016
DOI:10.1016/j.ssi.2016.09.027
•Nanocrystal cellulose (NCC) reinforced SFPAEKs composite proton exchange membranes presented better performances than SFPAEKs, such as proton conductivity and mechanical properties.•Nanocomposites were obtained with modified NCC and sulfonated fluorenyl-containing polyaryletherketones (SFPAEKs) for proton exchange membrane application via solution casting method.•NCC could be uniformly dispersed in the SFPAEKs matrix by controlling the NCC ratio.Sulfonated fluorenyl-containing polyaryletherketones (SFPAEKs) were synthesized through a postsulfonation approach under a mild reaction condition. The composite proton exchange membranes based on SFPAEKs and various amounts of the modified nanocrystalline cellulose (NCC) were prepared by solution casting method. The existence of the multiple hydroxyl and sulfonic acid groups on the chemically modified nanocrystalline cellulose was supposed to benefit the formation of hydrogen-bond network and proton-conducting channels, which would improve the proton conducting ability of the composite membranes. Furthermore, the properties, such as mechanical properties, thermal stability, water uptake, swelling ratio and so on, were thoroughly investigated. In comparison to the pristine SFPAEK, the composite membranes containing a “performance enhanced” NCC component presented the higher proton conductivity and better mechanical properties. It was found that the proton conductivity of the composite membrane with 4 wt% of NCC could reach 0.234 S cm− 1 at 100 °C, and this value was higher than that of most of the reported membranes. The results showed that the modified nanocrystalline cellulose reinforced SFPAEK composite membrane would be promising for the application as middle-temperature proton exchange membranes in fuel cells.
Co-reporter:Hengti Wang, Zhiang Fu, Wenyong Dong, Yongjin Li, and Jingye Li
The Journal of Physical Chemistry B 2016 Volume 120(Issue 34) pp:9240-9252
Publication Date(Web):August 9, 2016
DOI:10.1021/acs.jpcb.6b06761
Micellization of in situ formed graft copolymers during reactive blending is commonly observed. Numerous studies have been carried out to minimize the formation of micelles and enhance emulsification efficiency. Herein, we investigated the formation of interfacial Janus nanomicelles (JNMs) and their compatibilization effects on immiscible polymer blends when reactive graft copolymers (RGCs) are used as compatibilizers. Poly(styrene-co-glycidyl methacrylate)-graft-poly(methyl methacrylate) RGCs were synthesized and used as compatibilizers for immiscible poly(l-lactide) (PLLA)/poly(vinylidene fluoride) (PVDF) blends. Numerous nanomicelles were formed in situ during melt blending by grafting of PLLA onto the RGCs. The formation and location of JNMs depended not only on the molecular architecture of the RGCs but also on the melt processing sequence and molecular weight of the components. Interfacial JNMs can effectively improve the miscibility of polymer blends, thereby enhancing the performance of immiscible polymer blends.
Co-reporter:Chenyang Xing, Yanyuan Wang, Xingyi Huang, Yongjin Li, and Jingye Li
Macromolecules 2016 Volume 49(Issue 3) pp:1026-1035
Publication Date(Web):January 27, 2016
DOI:10.1021/acs.macromol.5b02429
Nanostructured polymeric dielectric composites, based on poly(vinylidene fluoride) (PVDF), conductive carbon black (CB), and an unsaturated ionic liquid (IL), 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIM][BF4]), were fabricated by melt blending and electron beam irradiation (EBI) methods. Our strategy forms simultaneous double nanophases in the PVDF matrix, that is, homogeneously dispersed CB nanoparticles and organic PVDF-g-IL nanodomains. The organic nanodomains were produced by microphase separation of the PVDF-g-IL chains from the PVDF matrix at melt state in the electron beam (EB) irradiated PVDF/IL-CB nanocomposites. Furthermore, the CB nanoparticles were fully adhered with these nanodomains, and novel structures with nanodomains@CB nanoparticle were achieved. Such nanodomains@CB nanoparticle structures showed a synergetic nucleating effect on the PVDF crystallization and led to the formation of dominant nonpolar α phases in the nano-PVDF/IL-CB composites. Because of the nanodomains adhesion of the CB nanoparticles, the nano-PVDF/IL-CB composites displayed a drastic reduction in dc conductivity compared with that of PVDF/CB and PVDF/IL-CB composites, respectively. Importantly, the resultant nano-PVDF/IL-CB composites exhibited significantly decreased losses relative to that of PVDF/CB, PVDF/IL, and PVDF/IL-CB composites. The structures of nanodomains@CB nanoparticle can be well responsible for this improvement of dielectric performance due to the fact that nanodomains confined the ion movements of IL in electric field and that their adhesion to the CB nanoparticle surfaces largely hindered the direct CB–CB nanoparticle contacts, thus decreasing their leakage currents. Our strategy not only fabricates PVDF/CB dielectric materials with good CB dispersion, higher dielectric permittivity, lower conductivity, and lower loss but also paves a new strategy for fabricating nanocomposites with double nanophases in polymer matrix.
Co-reporter:Lijun Ye, Cuicui Ye, Xianchun Shi, Hongyan Zhao, Kangyuan Xie, Depei Chen and Yongjin Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 33) pp:8510-8518
Publication Date(Web):10 Jul 2015
DOI:10.1039/C5TC01837D
In this work, we focus on exploring a new method to prepare conductive nanoporous polymeric materials, by simply incorporating multi-walled carbon nanotubes (MWCNTs) into melt-miscible poly(L-lactic acid)/poly(oxymethylene) (PLLA/POM) blends. The POM components in the ternary nanocomposites crystallize first to form “nano-hybrid shish-kebab (NHSK)” structures at a high temperature in the presence of MWCNTs, with the simultaneous exclusion of poorly crystallizable PLLA chains into the intra-NHSK regimes. The subsequent PLLA crystallization in the intra-NHSK regimes is also nucleated on the surface of MWCNTs and transforms the final crystal morphology into “ternary-hybrid shish-kebab (THSK)” superstructures. Therefore, a “binary-polymer-decoration” of MWCNTs, named “block-assembling”, is achieved. Such a novel “block-assembling” structure is further used to fabricate conductive nanoporous polymeric materials with a unique interposition structure of CNTs in the inner wall of the internal pores after the removal of the PLLA components in the ternary nanocomposites.
Co-reporter:Lijun Ye, Xianchun Shi, Cuicui Ye, Zhouli Chen, Mengmeng Zeng, Jichun You, and Yongjin Li
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 12) pp:6946
Publication Date(Web):March 16, 2015
DOI:10.1021/acsami.5b00848
Poly(oxymethylene)/poly(l-lactic acid) (POM/PLLA) blends are typical melt-miscible binary systems. During isothermal crystallization at various temperatures, in the presence of amorphous PLLA chains, POM crystallizes into banded spherulites with different band spaces, which forms a continuous crystalline phase and serves as a sturdy frame in the final porous materials. On the other hand, the amorphous PLLA chains are simultaneously expelled out from POM crystal lamellae to generate the other continuous phase during the crystallization of POM. Consequently, the interpenetration of the POM lamellae and the amorphous PLLA phase construct a cocontinuous phase structure. All the PLLA constituents are fully included in the interlamellar or interfibrillar of POM crystals. Thus, nanoporous POM materials with hierarchical patterned surface and 3D interpenetrated internal channels have been successfully obtained by extracting the amorphous PLLA phase. It is further found that the POM crystal morphologies in the blends are much dependent on the crystallization conditions. Therefore, the hierarchical patterned structure and the size of internal channels (pore size) can be modulated by adjusting the crystallization conditions.Keywords: crystallization; hierarchical patterned surface; melt-miscible crystalline/crystalline blend; nanoporous polymeric material
Co-reporter:Hengti Wang, Wenyong Dong, and Yongjin Li
ACS Macro Letters 2015 Volume 4(Issue 12) pp:1398
Publication Date(Web):November 30, 2015
DOI:10.1021/acsmacrolett.5b00763
Block or graft copolymers located at polymer–polymer interfaces have been considered as ideal compatibilizers for immiscible polymer blends. Herein, we report a novel compatibilization mechanism using Janus nanomicelles (JNMs) formed in situ at the polymer–polymer interface in immiscible polyvinylidene fluoride (PVDF)/polylactic acid (PLLA) blends. A small amount of a reactive graft copolymer, poly(styrene-co-glycidyl methacrylate)-graft-poly(methyl methacrylate) (P((S-co-GMA)-g-MMA)), is incorporated into the PLLA/PVDF blends by simple melt mixing. The in situ grafting of PLLA chains onto P((S-co-GMA)-g-MMA) during melt mixing leads to the formation of numerous JNMs with a shell structure consisting of PLLA and PMMA hemispheres. These JNMs are located at the PLLA/PVDF interface, where they behave as effective compatibilizers for the immiscible PLLA/PVDF blends. This interfacial micelle compatibilization (IMC) mechanism opens new opportunities to exploit interfacial emulsification using JNMs and should be of great significance in the compatibilization of polymer alloys.
Co-reporter:Wenyong Dong, Meifeng He, Hengti Wang, Fanglu Ren, Junqing Zhang, Xuewen Zhao, and Yongjin Li
ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 10) pp:2542
Publication Date(Web):August 26, 2015
DOI:10.1021/acssuschemeng.5b00740
A reactive comb (RC) polymer, which was composed of one poly(methyl methacrylate) (PMMA) backbone, two PMMA side chains and a few epoxy groups that distributed randomly along the backbone, was applied as a compatibilizer in an immiscible poly(l-lactic acid)/acrylonitrile-butadiene-styrene) system (PLLA/ABS). The morphological structures, the rheological, mechanical and thermal properties of the obtained PLLA/ABS blends were investigated systematically. For the first time in the reactive compatibilized system, we found that the glass transition temperature (Tg) of both PLLA and ABS phase depressed to lower temperature and the toughness of the compatibilized PLLA/ABS blend was significantly improved. The effect of blending composition showed that both the depression of Tg and the improvement of toughness were most significant at the weight ratio of 50/50, at which the area of PLLA/ABS interface was the largest. It is considered that the in-situ formed PLLA grafted RC polymers at the PLLA/ABS interface drastically improved the interfacial adhesion between the two phases. Thus the internal pressure, derived from the differentiation of the thermal contraction between the PLLA and ABS phase during cooling from the melt, significantly enhanced the mobility of the molecular chains of the both components on a microscopic scale, which was manifested by a double Tg depression phenomenon on a macroscopic scale. This investigation revealed that both the interfacial adhesion and asymmetric thermal shrinkage are important for the toughening of a rigid/rigid polymer blend.Keywords: Glass transition temperature; Interface; Poly(lactic acid); Reactive comb polymer; Reactive compatibilization;
Co-reporter:Xiaojun Cao, Kai Lu, and Yongjin Li
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 27) pp:6912-6921
Publication Date(Web):June 22, 2015
DOI:10.1021/acs.iecr.5b01478
The synergistic effects of organically modified montmorillonite (o-MMT) and magnesium hydroxide (MH) on the flame retardance and mechanical properties of a thermoplastic vulcanizate (TPV) have been investigated. The incorporation of more than 6 phr o-MMT induces a drastically decreased peak heat release rate and smoke production rate while simultaneously enhancing the mechanical properties of the TPV/MH composites. The improvements in both flame retardance and mechanical properties are attributed to the double role of o-MMT in the composites. On the one hand, the increase in viscosity due to o-MMT suppresses the vigorous bubbling caused by polymer pyrolysis. On the other hand, well-dispersed o-MMT serves as a rigid network that prohibits massive shrinkage of both the MH and TPV matrix during burning. Therefore, isolation of the protective chars by the clay network together with MgO is achieved, and such a structure prohibits heat and mass transfer during burning.
Co-reporter:Wenyong Dong, Hengti Wang, Meifeng He, Fanglu Ren, Tao Wu, Qianru Zheng, and Yongjin Li
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 7) pp:2081
Publication Date(Web):January 26, 2015
DOI:10.1021/ie503645a
Reactive comb (RC) polymers were synthesized by copolymerizing methyl methacrylate (MMA) with glycidyl methacrylate (GMA) and a kind of MMA macromer. The obtained molecules had both epoxide groups and long PMMA side chains distributed randomly along the PMMA backbone. The synthesized RC polymers were applied as compatibilizers in an immiscible poly(l-lactic acid)/poly(vinylidene fluoride) (PLLA/PVDF) system. Compared to their linear counterparts, only 1 wt % of RC polymers with appropriate length of side chains significantly reduced the size and enhanced the uniformity of the PVDF dispersed phase in PLLA matrix and the RC-compatibilized blends exhibited a significant improvement in fracture strain. The higher compatibilization efficiency of RC polymers was ascribed to the existence of PMMA side chains, which improved the stability of RC polymers at the interface of immiscible blend, and this was demonstrated by transmission electron microscopy.
Co-reporter:Lijun Ye;Cuicui Ye;Xianchun Shi;Hengti Wang;Hongyan Zhao;Xiaojun Cao;Jichun You;Yuanyuan Liang
Macromolecular Chemistry and Physics 2015 Volume 216( Issue 17) pp:1801-1807
Publication Date(Web):
DOI:10.1002/macp.201500196
Co-reporter:Kai Lu;Lijun Ye;Qiushi Liang
Polymer Composites 2015 Volume 36( Issue 7) pp:1258-1265
Publication Date(Web):
DOI:10.1002/pc.23030
Novel thermoplastic vulcanizate (TPV) based on two EVAs with different VA contents, ethylene vinyl acetate rubber (VA content =50 wt%; EVM) and ethylene VA copolymer (VA content =28 wt%; EVA28), has been successfully prepared by dynamic vulcanization in our previous work. In this study, we have incorporated aluminum hydroxide (ATH) into the TPV based on EVM/EVA28 for the purpose to fabricate halogen-free flame retardant TPVs with high flexibility. The morphology and the properties of the ATH filled TPVs have been investigated. It was found that the ATH particles were finely dispersed into the crosslinked EVM phase, while few ATH particles were observed in the EVA28 matrix. The fabricated TPVs with 45% ATH exhibit LOI of 30.2%, significantly prolonged ignition time, and drastically reduced heat release rate. At the same time, the TPVs show excellent stretchability (>300% elongation at break), nice elasticity (only about 30% remnant strain at 100% stretching), high strength, and good flexibility as well. We have attributed the multifunctional performance of the ATH filled TPVs to both the fine phase structure of the base TPVs and the selective dispersion of ATH fillers in the rubber phase. POLYM. COMPOS., 36:1258–1265, 2015. © 2014 Society of Plastics Engineers
Co-reporter:Chenyang Xing
The Journal of Physical Chemistry C 2015 Volume 119(Issue 36) pp:21155-21164
Publication Date(Web):August 3, 2015
DOI:10.1021/acs.jpcc.5b05349
Nanostructured polymeric composites, based on a homopolymer poly(vinylidene fluoride) (PVDF) and a small molecule, 1-vinyl-3-butylimidazolium chloride [VBIM][Cl], an unsaturated room-temperature ionic liquid (IL) have been fabricated. Our strategy forms organic conductive nanodomains with diameters of 20–30 nm dispersed homogeneously in the PVDF matrix. It is demonstrated that these conductive nanodomains are induced from microphase separation of the IL grafted PVDF (PVDF-g-IL) segments from the neat PVDF, which were produced by using electron-beam irradiation, leading IL molecules to graft onto the amorphous PVDF chains. It is also found that such microphase separation of PVDF-g-IL segments from PVDF matrix occurs only when the grafted IL content exceeds 3 wt %. Furthermore, the formed nanodomains enhance the crystallization rate of the matrix PVDF. The obtained nanostructured PVDF composites show dominant nonpolar α-phase of PVDF crystals and increased crystal long period (L) compared with neat PVDF. Additionally, the resulting nanostructured PVDF composites exhibit enhanced electrical properties, better Young’s modulus and ductility, and improved dielectric performance compared with neat PVDF, making the composites promising for potential use in superthin dielectric capacitors. The intriguing synthesis route will open up new opportunities for fabricating nanostructured polymer composites.
Co-reporter:Lijun Ye, Cuicui Ye, Kangyuan Xie, Xianchun Shi, Jichun You, and Yongjin Li
Macromolecules 2015 Volume 48(Issue 23) pp:8515-8525
Publication Date(Web):November 17, 2015
DOI:10.1021/acs.macromol.5b01904
Poly(l-lactic acid) (PLLA) and poly(oxymethylene) (POM), with very close melting temperatures (Tm), can crystallize simultaneously or separately in their blends depending on composition and crystallization temperature (Tc), resulting in various types of morphology. It is mainly attributable to the greatly different crystallization kinetics of PLLA and POM. At a content of POM (φPOM), 3 wt % < φPOM < 20 wt %, PLLA crystallization kinetics are comparable to POM, and therefore two type spherulites exhibit “side-by-side” simultaneous growth with the penetration of PLLA spherulites into POM crystals. Although crystal growth rate (vc) of POM is still a bit faster than that of PLLA, for φPOM = 3 wt %, the nucleation of POM is restrained and POM spherulites can only develop on the propagating PLLA growth fronts with the generation of novel “core–shell” blended spherulites. For 20 wt % ≤ φPOM < 80 wt %, interspherulitic growth of PLLA inside the pre-existing matrix of POM spherulites causes the formation of interpenetrated blended spherulites, owing to the large discrepancy in kinetics. At φPOM ≥ 80 wt %, PLLA molecular chains are redistributed into the interlamellar level regimes within the POM spherulites and can only crystallize into tiny crystals (owing to strong confinement). PLLA/POM blends provide a perfect example and new insights for understanding the crystallization of miscible crystalline/crystalline polymer blends (with very similar Tm’s), in which kinetic factors could play a significant role in crystallization behaviors and morphology.
Co-reporter:Chenyang Xing, Jipeng Guan, Yongjin Li, and Jingye Li
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 6) pp:4447
Publication Date(Web):March 5, 2014
DOI:10.1021/am500061v
Novel anti-static nanofibers based on blends of poly(vinylidene fluoride) (PVDF) and a room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], were fabricated using an electrospinning approach. The effects of the RTIL on the morphology, crystal structure, and physical properties of the PVDF nanofibers were investigated. Incorporation of RTIL leads to an increase in the mean fiber diameter and the rough fiber surface of the PVDF/RTIL composite nanofibers compared with the neat PVDF nanofibers. The PVDF in the PVDF/RTIL nanofibers exhibits an extremely high content (almost 100%) of β crystals, in contrast to the dominance of PVDF γ crystals in bulk melt-blended PVDF/RTIL blends. Nonwoven fabrics produced from the electrospun PVDF/RTIL composite nanofibers show better stretchability and higher electrical conductivity than those made from neat PVDF without RTIL, and are thus excellent antielectrostatic fibrous materials. In addition, RTIL greatly improved the hydrophobicity of the PVDF fibers, enabling them to effectively separate a mixture of tetrachloromethane (CCl4) and water. The extremely high β content, excellent antielectrostatic properties, better stretchability, and hydrophobicity of the present PVDF/RTIL nanofibers make them a promising candidate for micro- and nanoscale electronic device applications.Keywords: conductivity; crystals; electrospinning; ionic liquid; nanofibers; poly(vinylidene fluoride);
Co-reporter:Yuhang Cai, Mengmeng Zhao, Henti Wang, Yongjin Li, Zhigang Zhao
Polymer Degradation and Stability 2014 Volume 99() pp:53-60
Publication Date(Web):January 2014
DOI:10.1016/j.polymdegradstab.2013.12.012
Flame-retardant nanocomposites with high transparency based on poly (vinyl alcohol) (PVA) and pseudo-boehmite nanorods have been fabricated by synthesis of pseudo-boehmite nanorods and subsequent solution blending with PVA. The morphology and physical properties of PVA/pseudo-boehmite nanocomposites have been characterized systematically. Scanning electron microscopy investigations showed the homogeneous dispersion of pseudo-boehmite nanorods within PVA matrix even at very high nanorods loadings. The nanocomposites with 37.5 wt% pseudo-boehmite nanorods exhibit limit oxygen index (LOI) as high as 30.0 with the transmittance of more than 90% at the visible region and the enhanced refractive index. Moreover, the incorporation of the pseudo-boehmite nanorods increases the modulus and the tensile strength of PVA, indicating the significantly enhanced surface hardness of the nanocomposite. It is considered that the prepared PVA nanocomposites are not only useful as flame-retardant fibers, a long term pursued target for PVA fabrics, but also as optical appliances with its excellent transparency and high refractive index.
Co-reporter:Chenyang Xing, Xin Zheng, Liqun Xu, Jijun Jia, Jie Ren, and Yongjin Li
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 11) pp:4304-4311
Publication Date(Web):2017-2-22
DOI:10.1021/ie404096b
Transparent polymeric materials with high ductility and antistatic properties have attracted much attention. A room temperature ionic liquid (IL), tributyl(methyl)ammonium bis(trifluoromethane)sulfonylimide ([tbmam+][Tf2N–]), was integrated into polycarbonate (PC), to fabricate optically transparent antielectrostatic composites by melt processing. The morphology and physical properties of the composites were investigated. Differential scanning calorimetry and dynamic mechanical analysis indicated the depression of the glass transition temperatures of the PC/IL composites, compared with that of neat PC. This indicated the interaction between PC and the IL. Transmission electron microscopy indicated that the IL was highly compatible with PC, at low IL loadings. This resulted in enhanced antielectrostatic properties, and significantly improved elongation at break of the PC/IL composites. The PC/IL composites maintained the high transmittance of PC. In addition, the PC/IL composites with high clearance and antielectrostatic properties could be achieved by large-scale continuous melt extrusion, indicating that the method to fabricate both optically transparent and antielectrostatic composite is feasible for industrial application.
Co-reporter:Kai Lu, Xiaojun Cao, Qiushi Liang, Hengti Wang, Xiaowen Cui, and Yongjin Li
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 21) pp:8784-8792
Publication Date(Web):2017-2-22
DOI:10.1021/ie5008147
Magnesium hydroxide (MH) and an intumescent flame retardant (IFR) have been incorporated into a thermoplastic vulcanizate (TPV) for the purpose to fabricate halogen-free flame retardant elastomeric materials. Significant synergistic effects of MH and IFR have been observed for the TPV in terms of both flame retardant properties and mechanical performance. The mechanism of the synergistic effects has been investigated. The results indicate that a small amount of IFR accelerates the degradation of the matrix and induces a shrinkage matrix, leading to a compact and unbroken MgO protective layer. Such compact MgO layer on the surface of the material prevents the bulk material from further degradation, and a high flame retardant performance was achieved. Obviously, this novel flame retardant system paves new possibility for the high performance nonhalogen flame retardant polymeric materials and should also be applied to other polymers.
Co-reporter:Lijun Ye, Jishan Qiu, Tao Wu, Xianchun Shi and Yongjin Li
RSC Advances 2014 vol. 4(Issue 82) pp:43351-43356
Publication Date(Web):04 Sep 2014
DOI:10.1039/C4RA06943A
A “banded spherulite templated” strategy has been developed to fabricate 3-D interpenetrated nanoporous polymeric materials. Poly(oxymethylene) (POM) crystallizes into large banded spherulites with incorporation of poly(L-lactic acid) (PLLA) at high temperature. The amorphous PLLA components are simultaneously expelled out from the twisted POM crystal lamellae during the crystallization of the POM components. Therefore, a fully co-continuous phase structure is formed with the interpenetration of POM twisted lamellae and the amorphous PLLA phase. The nanoporous POM materials with high porosity and large specific surface area were successfully obtained after extracting the PLLA phase between the twisted POM lamellae. The 3-D interconnected nanoporous POM films obtained using this strategy could be used in various applications. Moreover, such a strategy should also be applicable to other polymer blend systems and it provides a new route for fabricating nanoporous polymeric materials.
Co-reporter:Wenyong Dong;Xiaojun Cao
Polymer International 2014 Volume 63( Issue 6) pp:1094-1100
Publication Date(Web):
DOI:10.1002/pi.4618
Abstract
High-performance biosourced poly(l-lactide) (PLLA)/polyamide 11 (PA11) (55/45) blends with small amounts of rubber, ethylene glycidyl methacrylate-graft-styrene-co-acrylonitrile (EGMA-g-AS), were fabricated by simple melt compounding. Epoxide groups in EGMA-g-AS are ready to react with both PA11 and PLLA, and thus EGMA-g-AS could be manipulated to locate mainly in either PA11 phase or PLLA phase by variation of the blending sequence. It was found that the blend with salami structure in which EGMA-g-AS is predominantly dispersed in the PLLA phase provides not only significantly improved tensile ductility, but also excellent film impact strength, while keeping relatively high modulus. The elongation at break and the film impact strength of such materials with 6 phr EGMA-g-AS are 322% and 361 kJ m−2, which are 78 and 5.2 times those of unmodified PLLA, respectively. In contrast, the blends with EGMA-g-AS mainly in the PA11 phase fracture in a brittle mode with low toughness. The toughening mechanism of the PLLA/PA11 blends with the sub-inclusion salami structure was investigated using a double-notch technique. The brittle-to-tough transition was observed on increasing the rubber sub-inclusion concentration in the PLLA phase. © 2013 Society of Chemical Industry
Co-reporter:Jishan Qiu, Jipeng Guan, Hengti Wang, Shanshan Zhu, Xiaojun Cao, Quan-lin Ye, and Yongjin Li
The Journal of Physical Chemistry B 2014 Volume 118(Issue 25) pp:7167-7176
Publication Date(Web):June 2, 2014
DOI:10.1021/jp412519g
Phase diagrams and glass transition behaviors of poly(l-lactic acid)/polyoxymethylene (PLLA/POM) blends have been investigated in our previous work (Macromolecules 2013, 46, 5806–5814). In this work, the crystallization behaviors and physical properties of the PLLA/POM blends with the PLLA as the major component have been systematically studied. POM was crystallized into the fragment crystals that were finely dispersed in the PLLA matrix when cooling down from the melt of the blends. It was found that the POM fragment crystals accelerated the crystallization process of PLLA matrix and increased the final crystallinity of PLLA significantly in the blends. At the same time, the PLLA spherulites nucleated by POM fragment crystals were much smaller than those obtained from neat PLLA. It was further found that the crystallization rate of PLLA was quite dependent upon the POM loadings and the highest crystallization rate was observed at POM loadings of 7 wt %. It is considered that the POM fragment crystals take the nuclei role to initiate the crystallization of PLLA at low POM loadings, while a high content of POM in the blends leads to the large POM spherulites that cannot nucleate PLLA crystallization effectively. The obtained PLLA/POM blends at low POM loadings with small PLLA spherulites exhibited excellent optical transmittance and good mechanical performance.
Co-reporter:Shuangshuang Zhang;Yu Zhu;Tongfei Shi;Hui Zhao;Jichun You
Journal of Polymer Science Part B: Polymer Physics 2014 Volume 52( Issue 19) pp:1243-1251
Publication Date(Web):
DOI:10.1002/polb.23541
ABSTRACT
Phase behaviors induced by solvent annealing in poly(methyl methacrylate) (PMMA) and poly(styrene-ran-acrylonitrile) (SAN) blend ultrathin films have been investigated by atomic force microscopy and grazing incidence small-angle X-ray scattering. Our results indicate that both the phase separation within the blend and the dewetting of the film induced by composition fluctuation take place upon the selective solvent annealing, producing complex structures containing upper droplets (of one phase) and mimic-films (of the other rich-phase). The use of acetic acid (the selective solvent for PMMA) generates PMMA mimic-film and SAN droplets, while the introduction of DMF (exhibiting better solubility for SAN) vapor results in the formation of SAN mimic-film and PMMA droplets. Essentially, the interaction at polymer/substrate interface, resultant wettability of selected component, solubility of PMMA and SAN in adopted solvent dominate not only the phase separation and the dewetting of the whole film but also the synergism of them. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1243–1251
Co-reporter:Jichun You, Wenjia Sheng, Keke Huang, Changmin Hou, Huijuan Yue, Bin Hu, Min Wang, Donglei Wei, Qingwen Li, Liping Zhao, Wenyong Dong, Zhigang Zhao, and Yongjin Li
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 6) pp:2278
Publication Date(Web):March 2, 2013
DOI:10.1021/am4003099
By coupling the self-assembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) containing titanium precursors with the electrospinning technique, novel cigarlike nanofibers with an outer-shell and inner-continuous-pore structure and resultant fabrics were fabricated. Different from typical porous metal oxides, the prepared high-surface-area nonwoven fabrics show excellent mechanical properties. Not only are these fabrics self-supporting over a large area, but they can also be cut using scissors, which is important for large-scale applications. Furthermore, as electrode materials in Li-ion batteries, these fabrics exhibit much higher charge/discharge capacity and cycle stability compared with the commercially available nanosized TiO2 (P25). The improved mechanical and electrochemical performances are attributed to the presence of an outer-shell, inner-bicontinuous structures (including continuous TiO2 frame and continuous nanopores) and hierarchical pores from the cigarlike nanofibers.Keywords: block copolymer; cigarlike; electrospinning; hierarchical porous; TiO2;
Co-reporter:Chenyang Xing, Mengmeng Zhao, Liping Zhao, Jichun You, Xiaojun Cao and Yongjin Li
Polymer Chemistry 2013 vol. 4(Issue 24) pp:5726-5734
Publication Date(Web):15 Jul 2013
DOI:10.1039/C3PY00466J
A room temperature ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], has been used to modify poly(vinylidene fluoride) (PVDF). The crystalline structures, miscibility, and physical properties of PVDF/IL blends were investigated systematically. It was found that the incorporation of IL into the PVDF leads to drastically increased γ crystal forms of PVDF by the interaction between the >CF2 and cationic ions. Moreover, IL is fully miscible with PVDF with the interaction parameter (χ12) of −2.84 calculated by the revised Nishi–Wang equation due to the drastic equilibrium melting temperature depression. Dynamic mechanical analysis (DMA) and small angle X-ray scattering (SAXS) results indicate that the IL molecules are inserted into the gallery of PVDF lamellae. A small amount of IL induces the appearance of the crystal-amorphous interface relaxation of PVDF, originating from the enrichment of IL distribution near the crystal-amorphous interface. The obtained PVDF/IL blends exhibit excellent mechanical performance with significantly increased ductility and good optical transmittance. In addition, the incorporation of IL into PVDF enhances the electrical conductivity of PVDF films greatly. Therefore, novel PVDF films with high transparency, excellent antistatic properties, and a highly polar crystal form fraction were successfully achieved.
Co-reporter:Yanchun Tang, Kai Lu, Xiaojun Cao, and Yongjin Li
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 35) pp:12613-12621
Publication Date(Web):August 2, 2013
DOI:10.1021/ie401853k
Ethylene vinyl acetate rubber (vinyl acetate (VA) content = 50 wt %) (EVM) and ethylene vinyl acetate copolymer (VA content < 50 wt %) (EVA) are polymers with a very similar chemical structure. In this study, a novel thermoplastic vulcanizate (TPV) based on EVM/EVA28 (VA content = 28 wt %) blend has been successfully fabricated by dynamic vulcanization due to the selective cross-linking of EVM. The morphologies and properties of the TPVs have been investigated. It was found that the cross-linked EVM phase and the thermoplastic EVA28 phase form a perfect cocontinuous structure with the rubber phase size of about 100 nm. The fabricated TPV exhibits not only excellent stretchability (>900% elongation at break), nice elasticity (only about 19% remnant strain at 100% stretching), and good flexibility but also superior oil resistance.
Co-reporter:Liping Zhao;Jishan Qiu;Xiaojun Cao;Wenyong Dong;Jichun You
Macromolecular Research 2013 Volume 21( Issue 4) pp:456-461
Publication Date(Web):2013 April
DOI:10.1007/s13233-013-1087-5
Co-reporter:Jishan Qiu, Chenyang Xing, Xiaojun Cao, Hengti Wang, Lian Wang, Liping Zhao, and Yongjin Li
Macromolecules 2013 Volume 46(Issue 14) pp:5806-5814
Publication Date(Web):July 11, 2013
DOI:10.1021/ma401084y
The poly(l-lactic acid)/poly(oxymethylene) (PLLA/POM) blends have been prepared by simply melt blending. The phase diagram, miscibility, glass transition temperatures, and physical properties have been investigated systematically. The PLLA/POM blends exhibit typical lower critical solution temperature (LCST) behaviors. PLLA and POM are miscible in the melt state at low temperature and become phase-separated at elevated temperatures. It was found that the weak interactions between the carboxyl groups of PLLA and methylene groups of POM (weak C–H...O hydrogen bonding) account for the miscibility of the two components. Although the PLLA/POM blends are homogeneous at the melt state in the miscible temperature region, two distinct glass transition temperatures are observed for the all blends when quenched from the homogeneous state. More surprisingly, both POM and PLLA exhibit the apparent glass transition temperature (Tg) depression in the blends, compared with Tgs of the neat polymers. The behaviors are totally different from other reported miscible or partially miscible polymer blends, in which Tgs shift to each other or merge into one glass transition temperature. The investigation indicates that the crystallization of POM in the blend induces the phase separation of PLLA/POM blends and forms novel morphologies with the interpenetrated (cocontinuous) PLLA and POM phases. The double glass transition temperature depression of both PLLA and POM in the blends originates from the mismatch thermal shrinkage during cooling down from the high temperature. Moreover, we observed the improved ductility of the PLLA/POM blends as compared with the neat PLLA and POM, which has been attributed to higher molecular mobility due to the glass transition temperature depression for both PLLA and POM in the blends.
Co-reporter:Liping Zhao, Yongjin Li, Jishan Qiu, Jichun You, Wenyong Dong and Xiaojun Cao
Nanoscale 2012 vol. 4(Issue 20) pp:6613-6621
Publication Date(Web):28 Aug 2012
DOI:10.1039/C2NR31401K
A reactive chemical bonding strategy was developed for the incorporation of a high mass loading of individual single-wall carbon nanotubes (SWCNTs) into an elastomeric matrix using a reactive ionic liquid as a linker. This method simultaneously prevented the agglomeration of SWCNTs and caused strong interfacial bonding, while the electronic properties of the SWCNTs remained intact. As a result, the high conductivity of the carbon nanotubes (CNTs) and the flexibility of the elastomeric matrix were retained, producing optimum electrical and mechanical properties. A composite material with a loading of 20 wt% SWCNTs was fabricated with excellent mechanical properties and a high conductivity (9500 S m−1). The method could be used to form transparent thin conductive films that could tolerate over 800 bend cycles at a bending angle of 180° while maintaining a constant sheet resistance.
Co-reporter:Jichun You, Hui Fu, Wenyong Dong, Liping Zhao, Xiaojun Cao, and Yongjin Li
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 9) pp:4825
Publication Date(Web):August 17, 2012
DOI:10.1021/am301161s
Polyvinylidene fluoride (PVDF)/acrylic copolymer (ACP) blends are a typical miscible crystalline/amorphous system over the whole composition range. Our previous investigation indicated that blend samples with controlled component ratios and crystallization conditions exhibit good shape memory properties (J. Phys. Chem. B2012, 116, 1256–1264). In this work, we systematically investigated the cold crystallization temperature effects on the crystal morphologies and the shape memory properties for the 50/50 blend. It was found that the quenched blend is an amorphous material with a low glass transition temperature. Annealing at temperatures above Tg of the blend induces crystallization of PVDF from the miscible amorphous PVDF/ACP phase, leading to an increased glass transition temperature of the blend. High annealing temperature results in large PVDF spherulites, while low annealing temperature produces tiny crystals in the blend. Furthermore, tiny crystals serve as the physical cross-link points and the amorphous regions among them act as the reversible phase for the blend materials during the mechanical deformations. Therefore, the PVDF/ACP blends with tiny crystals show not only high shape fixity but also excellent recovery ratios.Keywords: cold crystallization; physical cross-link; polymer blend; shape memory properties; tiny crystals;
Co-reporter:Wenyong Dong, Fanhui Jiang, Liping Zhao, Jichun You, Xiaojun Cao, and Yongjin Li
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 7) pp:3667
Publication Date(Web):June 19, 2012
DOI:10.1021/am3007577
Nanostructured polymer blends have attracted significant attention recently. In this paper, the poly(lactic acid) (PLLA)/ethylene-co-acrylic ester-co-glycidyl methacrylate (E-AE-GMA) rubber (80/20) nanoalloys and microalloys were fabricated by melt blending and the structure–property relationships of the prepared alloys were investigated. In the nanoalloys, the rubber domains are homogeneously dispersed in the PLLA matrix with the overall domain size of <100 nm. Such nanoalloys exhibit not only high transparency in the visible region, but also significantly improved ductility and impact strength, compared with neat PLLA. Moreover, the nanodomains in the PLLA matrix enhance the crystallization rate of PLLA drastically. The overall crystallization rate of the PLLA nanoalloy is even higher than that of the PLLA nucleated by talc. In contrast, the PLLA microalloy has a phase structure with the size of the rubber domains being in the micrometer to submicrometer scale. The microalloy is opaque and displays almost the same tensile strength and modulus as the nanoalloy, but much higher impact strength than the nanoalloy.Keywords: crystallization; microalloy; nanoalloy; PLLA; reactive blending;
Co-reporter:Chenyang Xing, Liping Zhao, Jichun You, Wenyong Dong, Xiaojun Cao, and Yongjin Li
The Journal of Physical Chemistry B 2012 Volume 116(Issue 28) pp:8312-8320
Publication Date(Web):June 18, 2012
DOI:10.1021/jp304166t
The impact of pristine multiwalled carbon nanotubes (MWCNTs), an ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], and the ionic liquid-modified MWCNTs (IL-MWCNTs) on the crystallization behavior of melt-crystallized poly(vinylidene fluoride) (PVDF) has been investigated. Pristine MWCNTs accelerate crystallization of PVDF as an efficient nucleation agent, while the formed crystals are mainly nonpolar α crystal form with few polar β crystals. Incorporation of only ionic liquid results in depression of the PVDF melt crystallization rate due to the miscibility of IL with PVDF but leads to a higher content of polar crystals (β and γ forms) than MWCNTs. The ionic liquid and MWCNTs show significant synergetic effects on both the nucleation and the formation of polar crystals for PVDF by melt crystallization. Addition of IL-MWCNTs not only improves the MWCNTs dispersion in PVDF matrix but also increases the overall crystallization rate of PVDF drastically. More important, the melt-crystallized PVDF nanocomposites with IL-MWCNTs show 100% polar polymorphs but no α crystal forms. To the best of our knowledge, this is the first report on the achievements of full polar crystal form in the melt-crystallized PVDF without mechanical deformation or electric field. The IL to MWCNTs ratio and the IL-MWCNTs loading content effects on the crystallization behavior of PVDF in the nanocomposites were also studied. It is considered that the specific interactions between >CF2 with the planar cationic imidazolium ring wrapped on the MWCNTs surface lead to the full zigzag conformations of PVDF; thus, nucleation in polar crystals (β and γ forms) lattice is achieved and full polar crystals are obtained by subsequent crystal growth from the nuclei.
Co-reporter:Jipeng Guan, Chenyang Xing, Yanyuan Wang, Yongjin Li, Jingye Li
Composites Science and Technology (18 January 2017) Volume 138() pp:98-105
Publication Date(Web):18 January 2017
DOI:10.1016/j.compscitech.2016.11.012
Co-reporter:Wenfeng Jiang, Yong Liu, Chunyang Yu, Shanlong Li, Yongjin Li and Yongfeng Zhou
Chemical Communications 2016 - vol. 52(Issue 53) pp:NaN8226-8226
Publication Date(Web):2016/05/13
DOI:10.1039/C6CC03445D
This study reports a new category of stimuli-responsive morphological transitions, i.e., from one morphology (e.g., vesicles) to another two different ones (e.g., nanosheets and nanofibers), by investigating the light-responsive self-assembly behaviour of a “latent double-amphiphilic” linear-hyperbranched supramolecular block copolymer.
Co-reporter:Lijun Ye, Cuicui Ye, Xianchun Shi, Hongyan Zhao, Kangyuan Xie, Depei Chen and Yongjin Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 33) pp:NaN8518-8518
Publication Date(Web):2015/07/10
DOI:10.1039/C5TC01837D
In this work, we focus on exploring a new method to prepare conductive nanoporous polymeric materials, by simply incorporating multi-walled carbon nanotubes (MWCNTs) into melt-miscible poly(L-lactic acid)/poly(oxymethylene) (PLLA/POM) blends. The POM components in the ternary nanocomposites crystallize first to form “nano-hybrid shish-kebab (NHSK)” structures at a high temperature in the presence of MWCNTs, with the simultaneous exclusion of poorly crystallizable PLLA chains into the intra-NHSK regimes. The subsequent PLLA crystallization in the intra-NHSK regimes is also nucleated on the surface of MWCNTs and transforms the final crystal morphology into “ternary-hybrid shish-kebab (THSK)” superstructures. Therefore, a “binary-polymer-decoration” of MWCNTs, named “block-assembling”, is achieved. Such a novel “block-assembling” structure is further used to fabricate conductive nanoporous polymeric materials with a unique interposition structure of CNTs in the inner wall of the internal pores after the removal of the PLLA components in the ternary nanocomposites.
![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)