THE EFFECT OF PREPARATION PROCESS OF PMDA-ODA-DR1 POLYIMIDE ON ITS 2ND-HARMONIC GENERATION CHARACTERISTICS

In situ second harmonic generation (SHG) observation of PMDA-ODA-DR1 p olyimide films prepared by different preparative procedures were studi ed to understand the effects of the residual acid and the imidization byproduct and the extent of imidization on the SHG characteristics of the PMDA-ODA-DR1 polyimides. PMDA-ODA-DR1 polyimides with or without r emoval of salt were also investigated to study the influence of remain ing triethyl hydrogen ammonium chloride salt on the SHG characteristic s and reliability of the polymers. A blue shift in the UV/vis spectrum during poling was observed for the low-temperature-baked film, but di d not occur for the high-temperature-baked film. Both high-temperature imidization and removal of the byproduct organic salt did not only im prove the poling efficiency of PMDA-ODA-DR1 polyimide as a SHG materia l, but also slowed down the relaxation of the film and made the film m ore reliable. (C) 1995 John Wiley and Sons, Inc.