KINETICS OF PHASE-TRANSITION IN LYOTROPIC LIQUID-CRYSTALLINE POLYMERS

A kinetic study on phase transitions from nematic mesophase to isotrop ic state for poly(p-benzamide) (PBA)/H2SO4 and poly(p-phenyleneterepht halamide) (PPTA)/H2SO4 SYStems was carried out by using depolarized li ght intensity (DLI) technique and polarised light microscopy (PLM) obs ervation. The order of phase transition and activation energy were eva luated. The results indicated that the phase transition for both PBA/H 2SO4 and PPTA/H2SO4 systems is a first-order transition, and the polym er concentration and molecular flexibility have significant influence on the activation energy of the phase transition. The influences of co ncentration and molecular flexibility were discussed on the basis of t he modified mean-field theory.