THERMODYNAMIC PROPERTIES OF CONCENTRATED-SOLUTIONS OF POLY(HEXYL ISOCYANATE), A LIQUID-CRYSTALLINE POLYMER

Osmotic pressure and sedimentation equilibrium measurements were made on isotropic solutions of poly(hexyl isocyanate), a stiff-chain polymer forming a lyotropic liquid crystal, to determine the osmotic pressure and the solvent chemical potential as functions of polymer concentration. The resulting data were used to test the validity of the theory of Khokhlov and Semenov of polymer liquid crystals, which was almost quantitative in predicting the isotropic-liquid crystal phase diagrams for reasonably stiff polymers. It was found that the second virial approximation with respect to free energy basic to this theory was only valid under limited conditions and the scaled particle theory of Cotter on spherocylinders was shown to be a promising alternative.