THE TIME-TEMPERATURE SUPERPOSITION OF THE RHEOLOGICAL PROPERTIES OF MAIN-CHAIN LIQUID-CRYSTALLINE POLYMERS

It is demonstrated that it is possible to realize rheological stationa ry states in nematic main-chain polymers. The only condition is first to cancel out the unknown thermal and mechanical history of the polyme r inducing by annealing the specific stable 'polydomain' structure of the nematic phase. Once that stable 'polydomain' structure achieved th e rheological data become reproducible but not time-temperature superp osable, the polydomain structure being different perturbed by shear at different temperatures. For time-temperature superposition first a we ll defined orientation has to be induced by shear using amplitudes hig her than those used for the mechanical-dynamic measurements. Due to th e long relaxation times in the nematic phase the realization of statio nary states requires up to several days, depending on the molecular we ight and sample preparation.