N-phenylmaleimide polymers for second-order nonlinear optics

Second-order nonlinear optical properties of the polymers of N-phenylmaleimides coupled with nonlinear optical (NLO) chromophores through urethane linkages were investigated. N-[4-(Azidocarbonyl)phenyl]-maleimide, the precursor of the isocyanato N-phenylmaleimide, was prepared and reacted with NLO chromophores, N-(4-nitrophenyl)-L-prolinol (NPP) or 4′-[(2-hydroxyethyl)methylamino]-4-nitrostilbene (ANS) to give monomer 5 or monomer 6. The monomers were polymerized and copolymerized with methyl methacrylate (MMA) and styrene (ST). The nonresonant linear electro-optic (EO) coefficients, r₃₃ values of the copolymers of 5 with MMA or ST corona-poled under 0.6 MV cm^-1 were found to be about 10-15 pm V^-1 when measured at 632.8 nm, and those measured at 830 nm were lower by 15-20%. The r₃₃ values of the copolymers of 6 with MMA measured at 632.8 nm and 830 nm were 25-35 pm V^-1 and 8-10 pm V^-1, respectively. The homopolymer of 5 showed the excellent thermal stability of the EO coefficient, which retained 85% of its original value when aged at 80°C for 48 h. The EO coefficients of the copolymers were 45-70% of their original values after 48 h at 80°C. At room temperature, no decay of r₃₃ values of all polymers was observed over a period of 1 month.