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.