Pressure dependence of the depoling temperature in nonlinear optical polymers

Second harmonic generation (SHG) was used to monitor the pressure dependence of the depoling temperature (T-d) in dye-doped, corona-poled poly(methyl methacrylate), polystyrene, and polycarbonate, The decay of the SHG signal emitted from these systems was monitored al lived hydrostatic pressures up to 3000 atm while the temperature was ramped at 10 degrees C/min. The depoling temperature increased 21-27 degrees C in the three systems, for every 1000 atm of applied hydrostatic pressure, The width of the transition also increased as a function of pressure. The shift in T-d as a function of pressure is used to interpret previous relaxation data in poled polymers, leading us to conclude that chromophore reorientation in nonlinear optical polymers is coupled to long range alpha-type relaxations near and above the glass transition temperature, T-g, and to secondary motions well below T-g.