Ultra-High-Tg Chromophoric Polyimides and Polyureas as High-Performance Nonlinear Optical Materials

ABSTRACTThree approaches to the construction of high-Tg polyimides and polyureas as second-order NLO materials are discussed. In the first approach, copolymerization of bismaleimides with o,o‚-diallylbisphenol-A followed by functionalization with high-β NLO chromophores using a Mitsunobu procedure yields, after poling and curing, a series of heavily crosslinked chromophoric polyimides with Tg values as high as 320°C and partially resonant χ(2) responses as high as 1.0×10-7 esu (42 pm/V at 1064 nm, 1.17 eV). In the second two approaches, copolymerization of the chromophore 4,5-bis(4‚-aminophenyl)-2-(4„- nitrophenyl)imidazole with bismaleimides or diisocyanates yields polyimides and polyureas with Tg values as high as 292°C and partially resonant χ(2)values as high as 0.62× 10-7 esu(25 pm/V at 1064 nm). It is found that careful attention to the details of curing and crosslinking during poling results in NLO- active matrices exhibiting negligible decay in ( on aging in air at 100°C for periods of 1,000-4,000 h. The imidazole based materials exhibit only about 10% χ(2) decay on aging for 100 h at 200°C under N2.