Elastic constants in dilute poly(styrene)/nematic liquid crystal solutions - effects of concentration and molecular weight

We utilized the light scattering from the anisotropy of turbidity (LSAT) method and evaluated, for the first time, the three elastic constants of dilute solutions of polystyrene (PS) in 4-pentyl-4'-cyanobiphenyl (5CB) nematic solvent. Within the solubility range of this system (less than 5%), the elastic constants of spiny (K-1), twist (K-2), and bend (K-3) of PS/5CB solution were determined as a function of concentration and molecular weight of PS solute. The experimental results showed a systematic diversion of the elastic constants and, in particular, a large increase in K-1 with increasing concentration and molecular weight of PS. The results are in agreement with the predicted theoretical models and other experimental data. Determination of K-i in polymer/nematic solutions with LSAT is a promising experimental approach to study the macromolecular chain structure of flexible, semi-flexible and rigid-rod polymers in anisotropic regimes. (C) 1999 Elsevier Science Ltd. All rights reserved.