Features of critical behavior of bend elastic constants of polymer liquid crystal near nematic-smectic A phase transition point

Alexander P. Filippov; Vjacheslav V. Suev

doi:10.1117/12.385713

12 May 2000 Features of critical behavior of bend elastic constants of polymer liquid crystal near nematic-smectic A phase transition point

Alexander P. Filippov, Vjacheslav V. Suev

Author Affiliations +

Proceedings Volume 4147, Liquid Crystals: Chemistry, Physics, and Applications; (2000) https://doi.org/10.1117/12.385713
Event: XIII International Conference on Liquid Crystals: Chemistry, Physics, and Applications, 1999, Krynica Zdroj, Poland

Abstract

The temperature dependences of the elastic splay K₁ and bend K₃ constants and birefringence (Delta) n of a comblike combined side- and main-chain polymer near nematic (N)--smectic A (S_A) phase transition were investigated using the method of the Freedericksz threshold transitions. Experiments were performed on a series of fractions in the range of molecular weight from 900 to 10200. The splay constant K₁ and birefringence (Delta) n have practically normal `nematic' temperature dependence in the investigated temperature range. For some fractions near the N$ARLRS_A transition, the bend constant K₃ exhibits a rapid increase with decreasing temperature, which is explained by the fluctuations of smectic order in the nematic phase. For high molecular weight fractions, the fluctuation-dependent part of K₃ varies as (T - T_N-SmA)^-(rho ) according to theoretical predictions. Hence, the values of critical exponent (rho) are very large (1.1 - 1.4). For low molecular weight fractions, no agreement is observed between the results obtained and theoretical predictions. The features of critical behavior of bend elastic constants of liquid crystal investigated may be explained by the molecular weight polydispersity of polymer fractions.

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Alexander P. Filippov and Vjacheslav V. Suev "Features of critical behavior of bend elastic constants of polymer liquid crystal near nematic-smectic A phase transition point", Proc. SPIE 4147, Liquid Crystals: Chemistry, Physics, and Applications, (12 May 2000); https://doi.org/10.1117/12.385713

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