Crosslinkable maleimide copolymers for stable NLO properties

Second-order, nonlinear optical polymers based on epoxy-substituted methylv inylisocyanates and N-substituted maleimides were synthesized and character ized with spectral and thermal analysis. The photocrosslinking and thermal- crosslinking reactions of copolymers with different chromophore contents we re studied. Thermally induced crosslinking during the poling process, perfo rmed at the glass-transition temperature (T-g), was prevented by T-g being decreased through the addition of a plasticizer. Electrooptic coefficients (r(33)), measured for crosslinked and noncrosslinked systems, had similar a bsolute values and relaxation dynamics. This behavior was explained in term s of the similar rotational mobility of the chromophore units and the pauci ty of crosslinking sites. (C) 2001 John Wiley & Sons, Inc.