Novel Y-type polyimide with highly enhanced thermal stability of second harmonic generation

3,4-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-4'-nitrostilbene dianhydride was prepared and reacted with 4,4'-(hexafluoroisopropylidene)dianiline to yield a novel Y-type polyimide containing the 3,4-dioxynitrostilbenyl group as an NLO-chromophore, which constituted part of the polymer backbone. The resulting polyimide was soluble in polar solvents such as acetone and N, N-dimethylformamide. The polymer exhibited good thermal stability up to 370 degrees C in the thermogravimetric analysis. The glass-transition temperature (T-g) obtained from the differential scanning calorimetry thermogram was near to 153 degrees C. The second harmonic generation (SHG) coefficient (d(33)) Of the poled polymer film at the fundamental wavelength of 1064 cm(-1) was around 2.15 x 10(-8) esu (9.01 pm/V). The dipole alignment exhibited exceptionally high thermal stability even at a temperature 30 degrees C above the T-g,T- and there was no SHG decay below 180 degrees C because of the partial main chain character of the polymer structure.