1996 Fiscal Year Final Research Report Summary
Molecular Aspects of Mesophase Formation of Polymer Liquid Crystals As Revealed by ^2H NMR Analyzes and PVT Measurements
| Project/Area Number |
07405045
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 | Tokyo Institute of Polytechnics |
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Principal Investigator |
ABE Akihiro Tokyo Institute of Polytechnics Department of Industrial Chemistry Professor, 工学部, 教授 (50114848)
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| Co-Investigator(Kenkyū-buntansha) |
HIRAOKA Kazuyuki Tokyo Institute of Polytechnics Department of Industrial Chemistry Lecturer, 工学部, 講師 (50267530)
UEMATSU Yoshiko Tokyo Institute of Polytechnics Department of Industrial Chemistry Professor, 工学部, 教授 (80064260)
IMAI Yoshio Tokyo Institute of Technlogy Department of Organic Materials Professor (50016557)
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| Project Period (FY) |
1995 – 1996
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| Keywords | mainchain liquid crystals / order-disorder transition / PVT properties / spacer conformation / conformational entropy / phase diagrams for binary mixtures / constant volume transition entropy / chiral spacers |
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| Research Abstract |
Our interest is to study the conformation and the thermodynamic role of flexible chains involved in an anisotropic environment. Mainchain-type liquid crystals (LC) involve flexible segments as a unit connecting two mesogenic cores. From the accumulated experimental data, transition entropies of such LCs at the nematic-isotropic interphase remain nearly invariant when divided by the number of spacers. Our study thus started from dimer and trimer model compounds having a spacer such as -O (CH_2)_nO- with n=9 and 10. These LCs can be synthesized with a precise constitution. Binary mixtures of these LCs allow us to investigate the effect of molecular weight distribution. The results of our research, supported by the Monbusho grant for a two-year period, are summarized as follows :
1. The ^2H NMR analysis provided a technique to elucidate the orientational order parameter of the individual components of a given mixture. When dimer or timer LCs were dissolved in a monomer LC,the order paramet
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er of the mosogenic units of the former were found to be lower than those of the monomeric LC.In the mainchain-type LCs, bond angles conneting the mosogenic units to the spacer play an important role in determining the orientational order of the mosogenic core.
2. The equation of state analysis (Flory's expression) indicated that the free volumes of the dimer and trimer LCs are about 20% of the core volume in the isotropic state just above the NI transition point. The volume changes at the NI transition were found to be about 10-20%.
3. Combined use of the ^2H NMR and PVT measurements revealed that variation of the spacer conformation is largely responsible for the latent entropy at the NI as well as CN transitions. This observation immediately suggests that the stereochemical constitution of the spacer involved in the mainchain LCs effectively determines various thermodynamic properties of the system. Along this line, computer design of chiral-spacers is in progress in our laboratory. Some of them have been synthesized and tested. Less
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