Nonrelaxing Second-Harmonic Generation From A Poly(2-Methoxy-5-Nitro-1,4-Phenylenevinylene-Co-2-Methoxy-1,4-Phenylenevinylene)

We have succeeded in preparing a new poled poly[(2-inethoxy-5-nitro-1,4-phenylenevinylene)-co-(2-methoxy-1,4-phenylenevinylene)] (poly(MNPV-co-MPV)) in thin film via an organic soluble precursor route. The precursor co-polymer was prepared by partial nitration of an organic soluble precursor homopolymer synthesized by the polymerization of 2-methoxyphenylene-1,4-bisCtetrahydrothiophenium bromide) followed by reaction with methanol. The random copolymer consists of 67.5 mole % of 2-methoxy-5-nitro-1,4-phenylenevinylene-vinylene unit and 32.5 mole % of 2-methoxy-1,4-phenylenevinylene unit. The precursor polymer film was heated stepwise in an electric field of 10s V/cm and transformed to the final poly conjugated polymer of 1.48 μm thick. This film shows a large second-harmonic generation(x (2)=1 × 10−6 esu) when it is measured in transmission with the Nd:YAG laser beam of the wave length of 1.064 μm at an angle of 90° to the film. Moreover, the film exhibits no decay in the SHG activity for more than 3 months even when the sample has a thermal history up to 100 °C.