MODE-COUPLING THEORY OF THE ISOTROPIC-NEMATIC TRANSITION IN SIDE-CHAIN LIQUID-CRYSTALLINE POLYMERS

Using a mode coupling technique we investigate the dynamics near the i sotropic-nematic transition in liquid crystalline sidechain polymers. While in mean field approximation one obtains z = 1 for the dynamical critical exponent z for the relaxation time of the order parameter, we get from mode coupling the value z = 1.5, a result which is in agreem ent with recent experiments done in Martinoty's group on two different classes of sidechain liquid crystalline polymers using electric and a coustic birefringence measurements. An analysis of recent measurements of the dynamic stress-optical coefficient in sidechain elastomers sho ws that mode coupling effects are also important in that case.