KINETICS OF PHASE-TRANSITION IN LYOTROPIC LIQUID-CRYSTALLINE POLYMERS

A kinetic study on phase transitions from nematic mesophase to isotropic state for poly(p-benzamide) (PBA)/H2SO4 and poly(p-phenyleneterephthalamide) (PPTA)/H2SO4 SYStems was carried out by using depolarized light intensity (DLI) technique and polarised light microscopy (PLM) observation. The order of phase transition and activation energy were evaluated. The results indicated that the phase transition for both PBA/H2SO4 and PPTA/H2SO4 systems is a first-order transition, and the polymer concentration and molecular flexibility have significant influence on the activation energy of the phase transition. The influences of concentration and molecular flexibility were discussed on the basis of the modified mean-field theory.