Band texture formation of sheared polymeric liquid crystalline state

Qian, Renyuan; Chen, Shouxi

doi:10.1002/masy.19920530131

Cited by 14 publications

(1 citation statement)

References 24 publications

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“…Still further, Dong et al [24] detected the disclinations with s = −1/2 and s = +1 and their director distribution under SEM by using the decoration technique of these lamellae and etching technique. Chen et al [22,25] reported firstly the banded texture decoration technique, and the nematic Schlieren texture of aromatic copolyester was decorated by banded texture, which was induced during cure. The disclinations with s = ±1/2, s = ±1 and s = −3/2, and inverse wall were studied using POM.…”

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confidence: 99%

Disclination and molecular director studies on bowlic columnar nematic phase using mosaic-like morphology decoration method

Dong

Chen

Zeng

et al. 2009

Sci. China Ser. B-Chem.

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Two bowlic cyclotriveratrylene CTV-1 and CTV-2, with different peripheral groups of -OCH 3 and -OCH 2 CH 3 for CTV-1 and -OCH 3 and -OCH 2 COOCH 3 for CTV-2, respectively, were synthesized by typical trimerization via a multistep sequence from vanillin. Both bowlic CTV molecules were thermotropic liquid crystals, and presented typical grainy textures of the nematic phase and homogeneous texture of the single domain nematic phase. It is of interest to observe the regular and beautiful mosaic-like morphologies after cooling from liquid crystalline phases, which appeared and vanished repeatedly in several circles of cooling and heating. The size of each mosaic was several dozens of micron. In nature, the mosaic-like morphologies are the optical pattern of cracks formed by the shrinking, due to the crystallization of frozen texture of nematic phases. By means of scanning electron microscopy, the mosaic-like morphologies were observed to consist of lamellae, and each mosaic is a rectangular multi-layer lamella, which is composed of packed single-layered lamellae. The fibrils in the diameter of about 1 μm were observed, which are the structural units of lamellae and would be the bundles of the bowlic molecular columns. The mosaic-like morphologies decorate the bowlic molecular columnar nematic phase, therefore, a novel mosaic-like morphologies decoration method was applied to reveal the director distribution of several kinds of point disclinations, such as s = +1(δ =0°and δ =90°) and s = ±1/2, and Nèel domain walls. It was shown that the bowlic molecular columnar nematic phase behaved as normal nematic phases; however, the basic structural units ordered were the bowlic molecular column or the bundles of bowlic molecular column (i.e. fibrils), but not the bowlic molecules themselves. The bowlic molecular columns acted as the rod-like molecules in a normal nematic phase. Therefore, a new term B CN (bowlic columnar nematic phase) is used to describe the anomalous nematic phase in this paper.

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Section: Figurementioning

confidence: 99%

Disclination and molecular director studies on bowlic columnar nematic phase using mosaic-like morphology decoration method

Dong

Chen

Zeng

et al. 2009

Sci. China Ser. B-Chem.

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Synthesis and lyotropic behavior of mesogen‐linked cellulose acetates

Zhang

et al. 2004

J of Applied Polymer Sci

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Three aromatic (p-carboxyl phenyl) esters, 4-(benzoyloxy) benzoic acid, 4-(4Ј-methylbenzoyloxy) benzoic acid, and 4-(4Ј-chlorobenzoyloxy) benzoic acid, were synthesized and they showed nematic monotropic or thermotropic behavior. The mesogen-linked cellulose acetates were first prepared by the reaction of aromatic (p-carboxyl phenyl) esters with cellulose acetate through esterification in the presence of N,N-dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). Their degrees of mesogenic unit substitution (DS -meso ) were between 0.27 and 0.41. It was found that they can form cholesteric lyotropic phases in dichloroacetic acid and their critical concentration was about 25 wt %.

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Evidence for the liquid‐crystalline state of poly(3‐hexylthiophene) melt

Qian

Chen

Song

et al. 1994

Macromol. Rapid Commun.

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For the soluble and/or fusible conducting polymers of conjugated chains of heterocyclic monomer units there is a good reason to expect to observe either a lyotropic or a thermotropic liquid-crystalline state. Even if the poly(3-hexylthiophene) (PHTH) chain in global sense is rather flexible '), the rigid blocks of a conjugation length six interposed by flexible blocks should behave like rigid mesogens connected by flexible spacers and form a liquid-crystalline phase. So far it did not succeed observing the liquid-crystalline state of conducting polymers except one case of a water-soluble alkali salt of poly(thiophene 3-alkylsulfonate) which forms a cloudy blue solution attributed to be a lyotropic mesophase'). However, no direct evidence was given. Very recently fully protonated polyaniline with camphorsulfonic acid was found to exist as a lyotropic liquid-crystalline phase3), without any schlieren texture.In our recent work on PHTH fractionated samples') we found that the melting ranges are very broad usually having a temperature span of some 10°C by visual observation and the melting point of PHTH varies significantly with its molecular weight as shown in Tab. 1, covering a difference of 80 "C for molecular weight changes from 1 * lo4 to 5 * lo5, which is rather unusual for a polymer. In the temperature range slightly above the melting point (m. p.) we tried carefully to observe in a polarizing optical microscope (POM) whether there is a texture typical of a thermotropic liquidcrystalline phase. The experiment failed to observe any schlieren texture of the melt. However, when we applied a gentle shear to the melt layer of a PHTH fraction E') with a weight-average molecular weight aw = 3,5 -lo4 sandwiched between two glass slides at 195 "C and then air-quenched to room temperature, we observed a banded texture typical of main-chain liquid-crystalline polymers 4). This banded texture appeared in apparently isolated domains of a few hundred pm size and the bands are Tab. 1. Melting points of poly(3-hexylthiophene) fractions Fraction Melting range in "C A B C D K a) M,: weight-average molecular weight.

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Band texture formation of sheared polymeric liquid crystalline state

Cited by 14 publications

References 24 publications

Disclination and molecular director studies on bowlic columnar nematic phase using mosaic-like morphology decoration method

Disclination and molecular director studies on bowlic columnar nematic phase using mosaic-like morphology decoration method

Synthesis and lyotropic behavior of mesogen‐linked cellulose acetates

Evidence for the liquid‐crystalline state of poly(3‐hexylthiophene) melt

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