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Liquid Crystalline Behavior (liquid + crystalline_behavior)
Selected AbstractsTailoring the liquid crystalline property via controlling the generation of dendronized polymers containing azobenzene mesogenJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2010Chang-An Yang Abstract The first- and second-generation dendronized polymers containing azobenzene mesogen were designed and successfully synthesized via free radical polymerization. The chemical structures of the monomers were confirmed by elemental analysis, 1H NMR, and 13C NMR. The molecular characterizations of the polymers were performed with 1H NMR and gel permeation chromatography. The phase structures and transition behaviors were studied using differential scanning calorimetry, polarized light microscopy, and small-angle X-ray scatter experiments. The experiment results revealed that the first-generation dendronized polymer exhibited liquid crystalline behavior of the conventional side-chain liquid crystalline polymer with azobenzene mesogen, that is, the polymer exhibited smectic phase structure at lower temperature and nematic phase structure at higher temperature. However, the second-generation dendronized polymers exhibited more versatile intriguing liquid crystalline structures, namely smectic phase structure at lower temperature and columnar nematic phase structure at higher temperature, and moreover, the phase structure still remained before the decomposition temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1149,1159, 2010 [source] Synthesis and self-assembly of helical polypeptide-random coil amphiphilic diblock copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008Shiao-Wei Kuo Abstract Three amphiphilic rod-coil diblock copolymers, poly(2-ethyl-2-oxazoline- b -,-benzyl- L -glutamate) (PEOz- b -PBLG), incorporating the same-length PEOz block length and various lengths of their PBLG blocks, were synthesized through a combining of living cationic and N -carboxyanhydride (NCA) ring-opening polymerizations. In the bulk, these block copolymers display thermotropic liquid crystalline behavior. The self-assembled aggregates that formed from these diblock copolymers in aqueous solution exhibited morphologies that differed from those obtained in ,-helicogenic solvents, that is, solvents in which the PBLG blocks adopt rigid ,-helix conformations. In aqueous solution, the block copolymers self-assembled into spherical micelles and vesicular aggregates because of their amphiphilic structures. In helicogenic solvents (in this case, toluene and benzyl alcohol), the PEOz- b -PBLG copolymers exhibited rod-coil chain properties, which result in a diverse array of aggregate morphologies (spheres, vesicles, ribbons, and tube nanostructures) and thermoreversible gelation behavior. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3108,3119, 2008 [source] Effect of stoichiometry on liquid crystalline supramolecular polymers formed with complementary nucleobase pair interactionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006Kelly A. Burke Abstract We report herein studies on the liquid crystalline behavior of a series of supramolecular materials that contain different ratios of two complementary symmetrically-substituted alkoxy-bis(phenylethynyl)benzene AA- and BB-type monomers. One monomer has thymine units placed at either end of the rigid mesogenic core, while the other has N6 -(4-methoxybenzoyl)-adenine units placed on the ends. Differential scanning calorimetric and polarized optical microscopy studies have been carried out on these systems. These studies show that the material's behavior is strongly dependent on its thermal history. As a result, the materials can exhibit, on heating, either a liquid crystalline phase, a crystalline phase, or the coexistence of crystalline and liquid crystalline regions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5049,5059, 2006 [source] Liquid Crystalline Ordering and Charge Transport in Semiconducting MaterialsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2009Wojciech Pisula Abstract Organic semiconducting materials offer the advantage of solution processability into flexible films. In most cases, their drawback is based on their low charge carrier mobility, which is directly related to the packing of the molecules both on local (amorphous versus crystalline) and on macroscopic (grain boundaries) length scales. Liquid crystalline ordering offers the possibility of circumventing this problem. An advanced concept comprises: i) the application of materials with different liquid crystalline phases, ii) the orientation of a low viscosity high temperature phase, and, iii) the transfer of the macroscopic orientation during cooling to a highly ordered (at best, crystalline-like) phase at room temperature. At the same time, the desired orientation for the application (OLED or field-effect transistor) can be obtained. This review presents the use of molecules with discotic, calamitic and sanidic phases and discusses the sensitivity of the phases with regard to defects depending on the dimensionality of the ordered structure (columns: 1D, smectic layers and sanidic phases: 2D). It presents ways to systematically improve charge carrier mobility by proper variation of the electronic and steric (packing) structure of the constituting molecules and to reach charge carrier mobilities that are close to and comparable to amorphous silicon, with values of 0.1 to 0.7,cm2,·,V,1,·,s,1. In this context, the significance of cross-linking to stabilize the orientation and liquid crystalline behavior of inorganic/organic hybrids is also discussed. [source] Synthesis and characterization of thermotropic liquid crystalline poly(aryl ether ketone) copolymers with pendant 3-(trifluoromethyl) phenyl groupsPOLYMER INTERNATIONAL, Issue 6 2006Guibin Wang Abstract Novel poly(aryl ether ketone) copolymers with pendant 3-(trifluoromethyl)phenyl groups were synthesized by the reaction of a crystal-disrupting monomer, 3-(trifluoromethyl)phenylhydroquinone (FH) and a mesogenic monomer, 4,4,-biphenol (BP) with 1,4-bis(p -fluorobenzoyl)benzene (BF). Thermotropic liquid crystalline behavior of the copolymers was investigated by means of differential scanning calorimetry, polarized optical microscope and wide-angle X-ray diffraction. As a result, the copolymers with the respective molar ratios of FH/BP/BF of 0/100/100,10/90/100 and 80/20/100,100/0/100 were semi-crystalline without liquid crystalline properties, and amorphous polymers, respectively. In contrast, copolymers with the molar ratio of FH/BP/BF of 20/80/100,70/30/100 had liquid crystalline characteristics. Interestingly, the formation of a highly ordered smectic phase was confirmed for copolymers with the molar ratio of FH/BP/BF of 20/80/100,50/50/100, respectively. All the liquid crystalline copolymers had a wide liquid crystalline temperature range (57,75 °C). Copyright © 2006 Society of Chemical Industry [source] | ||||||||||