NONLINEAR-OPTICAL ACTIVITY RELAXATION ENERGETICS IN A POLYETHER THERMOPLASTIC NONLINEAR-OPTICAL POLYMER WITH A HIGH GLASS-TRANSITION TEMPERATURE

A polyether polymer comprised of the 4-nitrophenyl hydrazone of bisphenol K and bisphenol A in a 50/50 comonomer ratio exhibits stable NLO activity at 100 degrees C for years. In an effort to understand the kinetics and energetics of relaxation, isothermal aging studies were done at 150 degrees C, 175 degrees C and 200 degrees C. Williams-Watts stretched exponential and Arrhenius analysis were used to determine the activation energy and prefactors. In addition, polymer relaxations were studied by dynamical mechanical analysis and dielectric spectroscopy. The conclusion from this work is that the energetics of orientational relaxation are that of a sub-Tg relaxation, or beta relaxation, consistent with a crank shaft motion of the chromophore about the polymer axis. However, this relaxation only turns on at temperatures very near the polymer Tg, where enough free volume is developed for the motion to occur. We have termed this a Tg assisted beta relaxation.