H-1-NMR SPECTROSCOPIC INVESTIGATION OF THE DYNAMICS OF DIRECTOR ROTATION IN A COMB-SHAPED LIQUID-CRYSTAL POLYMER

Wide-band H-1 NMR spectroscopy was used to investigate the kinetics of director rotation in a comb-shaped polymer nematic having cyanobiphen yl mesogenic groups in the side chains. The director rotation was foun d to conform to the following general features: the experimentally obs erved kinetics of director reorientation was interpreted in terms of t he monodomain model; coefficients of rotational viscosity versus tempe rature plots were satisfactorily described by the Arrhenius equation w ith abnormally high activation energies; activation energy increased w ith an increase in polymer chain length; the rotational viscosity coef ficient was related to polymer chain length via an exponential depende nce; an increase in temperature was accompanied by a linear increase o f the exponent from 0.9 to 2.2.