1 H NMR Spectroscopic Investigation of the Dynamics of Director Rotation in Comb-Shaped Liquid Crystal Polymers

Abstract

Wide-line 1 H NMR spectroscopy was used to investigate the kinetics of director rotation in the comb-shaped nematic polymer [CH 2 CH(COOR)] n (R= (CH 2 ) 4 OPhPhCN).The director rotation was found to conform to the following general features: the experimentally observed kinetics of director reorientation was interpreted in terms of the monodomain model; coefficients of rotational viscosity versus temperature plots were satisfactorily described by the Arrhenius equation with abnormally high activation energies; activation energy increased with an increase in polymer chain length; the rotational viscosity coefficient was related to polymer chain length via an exponential dependence; and an increase in temperature was accompanied by a linear increase of the exponent from 0.9 to 2.2