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961.
Po‐jen Yang Ling‐yung Wang Chieh‐yin Tang Hong‐Cheu Lin 《Journal of polymer science. Part A, Polymer chemistry》2010,48(4):764-774
Two series of banana‐shaped liquid crystalline (LC) H‐bonded complexes HPm / CBn (i.e., bent‐core H‐bonded side‐chain homopolymer HP mixed with bent‐core covalent‐bonded small molecule CB ) and CPm / HBn (i.e., bent‐core covalent‐bonded side‐chain homopolymer CP mixed with bent‐core H‐bonded small molecular complex HB ) with various m/n molar ratios were developed. The bent‐core covalent‐ and H‐bonded structural moieties were homopolymerized in the banana‐shaped LC H‐bonded complexes HPm / CBn and CPm / HBn , respectively. The influences of m/n molar ratios (polymeric moieties vs. small molecular moieties) on the mesomorphic and electro‐optical properties of both banana‐shaped LC H‐bonded complexes HPm / CBn and CPm / HBn were investigated. The polar smectic phases could be achieved and stabilized by smaller contents of polymeric dopants in banana‐shaped LC H‐bonded complexes, such as HP1/CB10 , HP1/CB15 , CP1/HB10 , and CP1/HB15 , which possessed tunable spontaneous polarization (Ps) values according to the molar ratios of m/n , that is, lower Ps values obtained in H‐bonded complexes HPm /CBn and CPm / HBn with higher ratios of H‐bonded moieties (larger m/n molar ratios), respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 764–774, 2010 相似文献
962.
963.
Jin‐Woo Choi Byoung‐Ki Cho 《Journal of polymer science. Part A, Polymer chemistry》2011,49(11):2468-2473
We studied the conducting and mesomorphic behavior of a dendritic‐linear copolymer on adding hydrophilic additives and lithium salts. For the preparation of the pristine block copolymer ( A ), a click reaction of a hydrophobic Y‐shaped dendron block and a hydrophilic linear poly(ethylene oxide) coil with Mn = 750 g mol?1 was performed. For ionic block copolymer samples ( 1–3 ), a hydrophilic compound ( B ) bearing two tri(ethylene oxide) chains was used as the additive. In all ionic samples, the lithium concentration per ethylene oxide was chosen to be 0.05. As characterized by polarized optical microscopy and small angle X‐ray scattering techniques, copolymer A showed a hexagonal columnar mesophase. On addition of lithium‐doped additives, ionic samples 1 and 2 with the additive weight fractions (fw) of 10 and 20%, columnar and bicontinuous structures coexisted in the liquid crystalline phase. On the other hand, ionic sample 3 with fw = 30% displayed only a bicontinuous cubic mesophase. Based on the impedance results, with increasing the amount of additives, the conductivity value increased from 3.80 × 10?6 to 2.34 × 10?5 S cm?1 at 35 °C. The conductivity growth could be explained by the interplay of the plasticization effect of the mobile additive and the morphological transformation from 1D to 3D of the ion‐conducting cylindrical cores. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
964.
Sourav Mete Krishna Gopal Goswami Priyadarsi De 《Journal of polymer science. Part A, Polymer chemistry》2020,58(5):766-778
To study the composition-dependent crystallization behavior of copolyperoxides, herein a series of copolymers were prepared by varying the ratios of methyl methacrylate (MMA) and 4-vinylbenzyl stearate (VBS) under 100 psi oxygen pressure using AIBN as an initiator at 50°C in toluene. Both 13C NMR and electron impact mass spectroscopy (EI-MS) approved an alternative placement of either of the monomer and peroxy (–O–O–) links throughout the polymer chain. Thermal stability of the resulting copolyperoxides was investigated by thermogravimetric analysis (TGA) and the degradation fragments have been recognized from EI-MS study. In addition, differential scanning calorimetry (DSC) displayed an endothermic peak as well as an exotherm associated with the melting of the side chain crystalline domains and degradation of –O–O– links in the polymer main chain, respectively. Furthermore, DSC thermograms unveiled a systematic decrease of the crystalline melting temperature (Tm) with the enhancement of MMA content in the copolymers. Small angle X-ray scattering (SAXS) revealed the existence of lamellar morphology (depends on VBS content in the copolyperoxide) in the synthesized polyperoxide materials, further supported by atomic force microscopy (AFM) analysis showing a layered fibrillar assembly with multiple heights of the lamella. The significant crystalline nature of the polyperoxides was further evidenced from the appearance of lattice fringes in the transmission electron microscope (TEM) micrographs. The crystalline morphology with birefringent texture was further evidenced from the polarized optical microscopy (POM) study. Thus, the present study reported the effective variation of crystalline behavior in copolyperoxide materials with the incorporation of MMA units in the copolyperoxide chains. 相似文献
965.
Dr. Meihui Su Xiaosa Yan Xia Guo Quanwen Li Yushi Zhang Prof. Changhua Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(20):4505-4509
Dye assemblies exhibit fascinating properties and performances, both of which depend critically on the mutual packing arrangement of dyes and on the supramolecular architecture. Herein, we engineered, for the first time, an intriguing chlorosome-mimetic 2D crystalline J-dimer lamellar structure based on halogenated dyes in aqueous media by employing two distinct orthogonal halogen-bonding (XB) interactions. As the only building motif, antiparallel J-dimer was formed and stabilized by single π-stacking and dual halogen⋅⋅⋅π interactions. With two substituted halogen atoms acting as XB donors and the other two acting as acceptors, the constituent J-dimer units were linked by quadruple highly-directional halogen⋅⋅⋅halogen interactions in a staggered manner, resulting in unique 2D lamellar dye assemblies. This work champions and advances halogen-bonding as a remarkably potent tool for engineering dye aggregates with a controlled molecular packing arrangement and supramolecular architecture. 相似文献
966.
Masaki Moritsugu Tomomi Shirota Shoichi Kubo Tomonari Ogata Osamu Sato Seiji Kurihara 《Journal of Polymer Science.Polymer Physics》2009,47(20):1981-1990
Photo‐chemically tunable photonic band gap materials are prepared by infiltration of liquid crystal polymers having azobenzene groups into voids of SiO2 inverse opal films. Linearly polarized (LP) light irradiation results in transformation from a random to an anisotropic molecular orientation of azobenzene side chains in the voids of the SiO2 inverse opal film, leading to the reversible and stable shift of the reflection peak to longer wavelength more than 15 nm. To improve switching properties, we use copolymers of azobenzene monomer and tolane monomer, which have higher birefringence, as infiltration materials into the voids. The azobenzene‐tolane copolymers are found to show higher birefringence than azobenzene homopolymers by the LP light irradiation at higher temperature. Consequently, the reflection band of the SiO2 inverse opal film infiltrated with the azobenzene‐tolane copolymer can be shifted to longer wavelength region more than 55 nm by the irradiation of LP light. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1981–1990, 2009 相似文献
967.
Chemical compositions, crystalline structures and thermal properties of bombax cotton and natural colored cottons including
laurel green, bottle green and brown cotton were investigated by chemical analysis, SEM, IR spectra and X-ray diffraction.
The results showed that the crystallinity and crystallite sizes of laurel green cotton were lower than those of bottle green
cotton because of the excess content of suberin in the former. The crystallinity of brown cotton was similar to that of white
cotton, and bombax cotton had the lowest crystallinity but its crystallite orientation was the highest. Thermal property of
bottle green cotton was the most stable, whose decomposition temperature was higher of 30°C than that of common white cotton
because of its higher lignin content, and bombax cotton had the lowest thermal degradation temperature. But bottle green cotton
reached the highest decomposition speed and made decomposition finish within a very short time, and bombax cotton was just
the reverse. 相似文献
968.
Hui Li Lei Wang Bin Zhao Ping Shen Songting Tan 《Journal of polymer science. Part A, Polymer chemistry》2009,47(13):3296-3308
A series of novel liquid‐crystalline copolymers based on fluorene and triphenylamine‐containing oligo(p‐phenylenevinylene) derivatives have been synthesized according to the Suzuki polymerization method. The structures, optical and electrochemical properties of the copolymers were characterized by 1H NMR, 13C NMR, GPC, UV–vis, photoluminescence (PL) spectroscopy, and cyclic voltammetry (CV), respectively. The thermotropic phase behavior of the copolymers was investigated by using differential scanning calorimetry (DSC) and polarized optical microscope (POM). All of the copolymers exhibit thermally liquid crystalline properties and represent the characteristic Schlieren textures in a wide temperature range. The effects of the concentrations and chain length of the oligo(phenylenevinylene) units on the thermal properties, liquid crystalline, photo‐ and electroluminescent properties of the copolymers have been investigated in details. Among the copolymers‐based devices with a configuration of ITO/PEDOT:PSS/polymers/Ca/Al, the device based on PF‐LOPV05 exhibits the lowest turn‐on voltage of 3 V and the maximum brightness of 210 cd/m2 at 8.3 V. A single layer device based on the blend of PF/PF‐LOPV05 emits white electroluminescence with CIE coordinates of (0.30, 0.35) at 8 V. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3296–3308, 2009 相似文献
969.
Jui‐Hsiang Liu Yen‐Ling Chou Rathinam Balamurugan Kai‐Hsin Tien Wen‐Tung Chuang Ming‐Zu Wu 《Journal of polymer science. Part A, Polymer chemistry》2011,49(3):770-780
Thermotropic chiral nematic (N*) side‐chain copolymers (CPs) bearing cholesteryl and azobenzene units were synthesized to investigate the structure–property relationships of the acrylates of the chiral, achiral, and photochromic monomers of free radical polymerization‐derived polymers. The polar effect of chlorine substitution on the benzene ring of the chiral monomer (M3*) widened the mesophase transition temperature only at the monomer level, but no remarkable effect on the mesomorphic, optical or thermochromism of the corresponding CPs was observed. An examination of the CPs prepared using differential scanning calorimetry and hot‐stage polarizing microscopy showed that all the CPs exhibited a cholesteric nematic phase (N*), and increasing the content of the cholesteryl units in the CPs displayed only the N* phase over a much wider temperature range. On cooling from the isotropic melt of N* CPs, selective reflections of visible light that changed from short to long wavelengths were observed. The photolysis of CPs revealed that CP1 – CP4 undergo reversible photoisomerization and that CP5 and CP6 undergo irreversible photoisomerization. The rate of isomerization depends on the type (? N?N? , ? CH?CH? , and both) and content of photochromic units in the CPs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
970.
Sharon Chen Sheng‐Hao Hsu Ming‐Chung Wu Wei Fang Su 《Journal of Polymer Science.Polymer Physics》2011,49(4):301-309
A new class of nanocomposite has been fabricated from liquid crystalline (LC) epoxy resin of 4,4′‐bis(2,3‐epoxypropoxy) biphenyl (BP), 4,4′‐diamino‐diphenyl sulfone (DDS), and multiwalled carbon nanotubes (CNTs). The surface of the CNTs was functionalized by LC epoxy resin (ef‐CNT). The ef‐CNT can be blended well with the BP that is further cured with an equivalent of DDS to form nanocomposite. We have studied the curing kinetics of this nanocomposite using isothermal and nonisothermal differential scanning calorimetry (DSC). The dependence of the conversion on time can fit into the autocatalytic model before the vitrification, and then it becomes diffusion control process. The reaction rate increases and the activation energy decreases with increasing concentration of the ef‐CNT. At 10 wt % of ef‐CNT, the activation energy of nanocomposite curing is lowered by about 20% when compared with the neat BP/DDS resin. If the ef‐CNT was replaced by thermal‐insulating TiO2 nanorods on the same weight basis, the decrease of activation energy was not observed. The result indicates the accelerating effect on the nanocomposite was raised from the high‐thermal conductivity of CNT and aligned LC epoxy resin. However, at ef‐CNT concentration higher than 2 wt %, the accelerating effect of ef‐CNTs also antedates the vitrification and turns the reaction to diffusion control driven. As the molecular motions are limited, the degree of cure is lowered. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献