Synthesis of nonlinear optical maleimide copolymer by polymer reaction andtheir electro-optic properties

Thermally stable poly(alpha-methyl styrene-co-maleimide) (MSMI) and poly(al pha-methyl styrene-co-4-carboxyphenyl maleimide) (MSCM) substrate polymers were obtained readily by free radical polymerization of comonomers. Introdu ction of a DR1 chromophore to the maleimide units of MSMI substrate polymer by the Mitsunobu reaction was dependent on the reaction solvent. The degre e of substitution of DR1 into the MSMI polymer was bound to be 91.1 mol % a nd 0.4 mol % by UV spectrometers in the THF and DMF solvent, respectively. DR1 chromophore was, however, substituted in the MSCM polymer at 33.0 mol % by Mitsunobu reaction in the THF solvent. Both substrate and NLO polymer e xhibited high thermal stability due to the incorporation of maleimide units in the polymer chain. The glass transition temperature (T-g) and initial d ecomposition temperature (T-i) of the NLO polymer were in the range of T-g = 185 degrees C and T-i = 310-345 degrees C. The electro-optic coefficient (r(33)) of NLO polymer was determined with an experimental setup capable of the real-time measurement while varying both the poling field and temperat ure. The NLO polymer MSMI-THF had a higher r(33) value than MSCM-DR due to an increased degree of substitution of DR1 chromophore. MSMI-THF had a maxi mum r(33) value of 16 pm/V at 135 MV/m poling field with a 632.8 nm light s ource. (C) 1999 John Wiley & Sons, Inc.