NONRELAXING 2ND-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-methoxy-5-nitro-1,4-pheny lenevinylene)-co-(2-methoxy-1,4,-phenylenevinylene)](poly(MNPV-co-MPV)) in thin film via an organic soluble precursor route. The precursor copolymer was prepared by partial nitration of an organic soluble precursor homopolymer synthesized by the polymerization of 2-methoxyphenylene-1,4-bis(tetrahydrothiophenium bromide) followed by reaction with methanol. The random copolymer consists of 67.5 mole % of 2-methoxy-5-nitro-1,4-phenylene-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 10(5) V/cm and transformed to the final polyconjugated polymer of 1.48 mu m thick. This film shows a large second-harmonic generation(chi((2))=1X10(-8) esu) when it is measured in transmission with the Nd:YAG laser beam of the wave length of 1.064 mu m at an angle of 90 degrees 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 degrees C.