1996 Fiscal Year Final Research Report Summary
Development and Dynamics of Liquid Crystalline Structures Studied by Heterodyne Dynamic Light Scattering Spectroscopy
| Project/Area Number |
07651108
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
高分子構造・物性(含繊維)
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
TSUNASHIMA Yoshisuke Kyoto University, Institute for Chemical Research, Associate Professor, 化学研究所, 助教授 (30089130)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Heterodyne method / Lyotropic liquid crystals / Dynamic light scattering / Cellulose acetates / Dimethylacetamide / Selfassembly / Selfassembly / Conformational transition |
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| Research Abstract |
The transition from the isotropic to anisotropic phase occured in lyotropic liquid crystalline polymers such as celllulose acetates were examined in view of the polymer chain stiffness, the chain dynamics, and the intermolecular associations which depend strongly on the polymer concentration in solution and on the solvent quality. The critical concentration v_2 where the lyotropic liquid crystals (LLC) appear was 24-26wt% for cellulose triacetates (CTA,degree of substitution DS=2.9) and higher for cellulose diacetates (DS=2.40) in trifluoroacetic acid (TFA), whereas in demethylacetamide (DMAc) v_2 was more than 50wt% for CTA and 45wt% for CDA.LLC was never observed for CTA in chloroform and for CDA in dimethylformamide. The difference in v_2 with solvents indicates that CTA and CDA take a molecular conformation specific to the solvent. Indeed, the chain stiffness of CTA and CDA analyzed on the basis of the wormlike chain model revealed that they are semiflexible chains with q=10 and 8
… More
nm in TFA and DMAc, respectively, and flexible chains in other solvents. Here q is the persistence length which represents the chain stiffness. Dynamic light scattering measurements for CDA fractions in DMAc in the dijute and semidilute solution regions showed that the CDA single molecule coexists with the intermolecular associations which may be formed with the hydrogen bonding between the intermolecular C-6 position OHs in the glucose unit. The CDA association was in two states, the selfassembly of four (State II) and 13-40 (State III) times as long as the single CDA chain. State II transformed to State III with increasing the CDA concentration. In addition, State III took three states, depending on the CDA concentration ; a long rigid-like structure and two huge structures, the latter being not so rigid and long as the former. The former long-rigid structure is considered to be a prototype of LLC formed by CDA in DMAc. The selfassemblies described above, however, disappeared in the external field such as the viscometric shear and the ultracentrifugal fields : the associations might be transient structures which cann't be retained under weak forces and collapse easily to a single chain. It is interesting that the CDA has a conformation six times stiffer than that in the shear field. Less
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