Properties of ultrahigh-Tg chromophoric polyimides and polyureas as high-performance nonlinear optical materials: architecture-processing-temporal stability relationships

摘要

Three complementary approaches to the construction of electric field polable high-Tg (glass transition temperature) polyimides and polyureas as second-order NLO materials are discussed. In the first approach, copolymerization of bismaleimides with o,o$PRM@- diallylbisphenol A followed by functionalization with high-$beta NLO chromophores using a Mitsunobu procedure yields, after poling and curing, a series of heavily crosslinked chromophoric polyimides with Tg values as high as approximately 260$DGR@C and $chi$+(2)$/ responses as high as 1.0 $MUL 10$+$MIN@7$/ esu (42 pm/V at $lambda$-o$/ $EQ 1064 nm, 1.17 eV). In the second two approaches, copolymerization of the chromophore 4,5-bis(4$PRM@aminophenyl)-2-(4'-nitrophenyl)imidazole with bismaleimides or diisocyanates yields polyimides and polyureas with Tg values as high as 292$DGR@C and partially resonant $chi$+(2)$/ values as high as 0.62 $MUL 10$+$MIN@7$/ esu (25 pm/V at $lambda$-o$/ $EQ 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 $chi$+(2)$/ on aging in air at 100$DGR@C for periods of 1000 - 4000 h. The imidazole- based materials exhibit only approximately 10% $chi$+(2)$/ decay on aging for 100 h at 200$DGR@C under N$-2$/.