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Crystalline Behavior (crystalline + behavior)

Distribution by Scientific Domains
Polymers and Materials Science100%

Kinds of Crystalline Behavior

  • liquid crystalline behavior
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    Selected Abstracts

    Tailoring the liquid crystalline property via controlling the generation of dendronized polymers containing azobenzene mesogen

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2010
    Chang-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 copolymer

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008
    Shiao-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 interactions

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006
    Kelly 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 Materials

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2009
    Wojciech 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]

    Effect of zeolite 5A on the crystalline behavior of polypropylene (PP) in PP/,-nucleating agent system

    POLYMER COMPOSITES, Issue 12 2008
    Zhiping Lv
    The effect of zeolite 5A on the crystalline behavior of polypropylene (PP) in PP/,-nucleating agent system was investigated with X-ray diffractometer (XRD), differential scanning calorimeter (DSC), and polarized light microscope (PLM) in this study. Zeolite 5A has less effect on crystalline phase of PP/,-nucleating agent than does n -CaCO3, which is ascribed to the stronger surficial polarity and better dispersibility of zeolite 5A. The data of DSC indicated that the crystallization peak temperature of PP increases by 8.3°C in the presence of zeolite 5A, and n -CaCO3 increases 5.7°C in PP/TMB-5 system, relative to pure PP. And the initial crystallization temperature (Tc0) and the relative crystallinity (Xc) of PP is much more dramatically raised in the presence of zeolite 5A than CaCO3. The efficiency of zeolite 5A in reducing the spherulites size of PP was seen clearly from the PLM photographs. The mechanical testing results showed that the flexural strength and impact strength of PP/,-nucleating agent system increased in the presence of zeolite 5A. POLYM. COMPOS., 2008. © Society of Plastics Engineers [source]

    Synthesis and characterization of thermotropic liquid crystalline poly(aryl ether ketone) copolymers with pendant 3-(trifluoromethyl) phenyl groups

    POLYMER INTERNATIONAL, Issue 6 2006
    Guibin 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]

    The Effects of the Modified Starches on the Melting Flow and Biodegradation of the Starch/Glycerol Blend

    MACROMOLECULAR SYMPOSIA, Issue 1 2008
    Chia-I Liu
    Abstract Summary: The purpose of this study was to improve the melting flow of starch/glycerol(GA) blends by modified starches. A variety of modified starches, which was treated by hydrolysis and acid hydrolysis, with and without ultrasonic treatment were used. The MFI (melt flow index) of blends increased from 0.5g/10min to 300g/10min when the addition of acid hydrolysis starch (0.3M CA-starch) was 70wt%. Their crystalline behaviors were analyzed by XRD results. The ultrasonic treatment has been proved to have the effect of hydrolysis without acids and synergistic effect on recrystalline. The SEM micrographs of the blend with the ultrasonic treatment starch gave the cleaving surface with comparison to the other blends. The weight loss of the blends with acid hydrolysis starches reached to 60,80% after one week biodegradation as the ultrasonic treatment was used. [source]