Synthesis and Nonlinear Optical Properties of Novel Y-type Polyimides with Highly Enhanced Thermal Stability of Second Harmonic Generation

Abstract

ABSTRACT 2,3-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-4′-nitrostilbene dianhydride ( 4 ) was prepared and reacted with 4,4′-oxydianiline and 4,4′-diaminobenzanilide to yield unprecedented novel polyimides 5–6 containing 2,3-dioxynitrostilbenyl groups as NLO-chromophores, which constituted parts of the polymer backbones. The resulting polyimides 5–6 were soluble in polar solvents such as DMSO and DMF. Polymers 5–6 showed a thermal stability up to 300°C in TGA thermograms with T g values from DSC thermograms in the range of 135–141°C. The SHG coefficients (d 33) of poled polymer films were around 6.14 × 10−9 esu. The dipole alignment of poled polymer films exhibited exceptionally high thermal stability even at 30°C higher than T g and there was no SHG decay below 170–190°C due to the partial main chain character of polymer structure, which was acceptable for NLO device applications.