MAIN-CHAIN NONLINEAR-OPTICAL POLYMERS WITH ENHANCED ORIENTATIONAL STABILITY

Polyamides based on 2',5'-diamino-4-(dimethylamino)-4'-nitrostilbene ( DDANS) and aliphatic diacids, and polyamideesters based on DDANS, xyet hyl)amino)-benzaldehyde-1,1-diephenylhydrazone (BBDH), and adipic acid represent a promising class of polymers for nonlinear optic (NLO) and photorefractive applications, where the nonlinear optical units are f ixed in the polymer backbone with their dipole moments oriented transv ersely to the main chain. The orientational relaxation behavior of a s eries of random copolymers and block copolymers was investigated at di fferent temperatures below the glass transition by the decay of the no nlinear optical susceptibilities of corona-poled thin films. The time dependence of the decay was found to be well represented by the Kohlra usch-Williams-Watts stretched-exponential function. The temperature de pendence of the decay could be correlated with the glass transition te mperature T-g using a normalized relaxation law with (T-g - T)/T as th e relevant scaling parameter. The investigation of the thermal stabili ty of the NLO-phore received special attention in this study. The main -chain polymers investigated exhibit an enhanced orientational stabili ty when compared to side-chain or guest-host systems.