Journal of Polymer Science Part A: Polymer Chemistry, Vol.37, No.5, 513-524, 1999
Synthesis and characterization of copolymaleimides containing 4-cyanobiphenyl-based side groups for nonlinear optical applications
We report the synthesis of a nematic copolymer, P(CBMS-co-M-3), prepared by free radical polymerization of an equimolecular mixture of p-(4-cyanobiphenyl-4＇-yloxy)methylstyrene (CBMS) and N-[3-(4-cyanobipheny1-4＇ -yloxy)propyl] maleimide (M-3,) and two isotropic alternating copolymers, P(S-alt-M,) (n = 3,6) prepared by chemical modification of poly(styrene-alt-maleimide), P(S-alt-M), by n-(4-cyanobiphenyl-4＇-yloxy)alkan-1-ol. These copolymaleimides were characterized by NMR, DSC, and optical microscopy. Some corona poling experiments were performed and the second harmonic coefficients d(31) and d(33) were measured. It was shown that one can gain in net polar ordering by starting with a liquid crystalline system. The ratio d(33)/d(31) was much larger than 3, in agreement with the molecular statistical models for electric field poling of liquid crystals. At ambient conditions, changes of d(33) and d(31) are 15% over 325 days.