Ultrahigh-temperature polymers for second-order nonlinear optics. Synthesis and properties of robust, processable, chromophore-embedded polyimides

A general, convergent approach to the synthesis of a series of stilbene- an d ate-based donor-acceptor, second-order nonlinear optical (NLO) chromophor es is reported. The synthetic strategy enables preparation of both acid- an d base-reactive structures, yielding protected, diamine-functionalized chro mophores which can be liberated using either acidic or alkaline regents for incorporation into polyimide backbones. Three such chromophores, bis(4-ami nophenyl)[4-(2-(4-nitrophenyl)vinyl)phenyl]amine, bis(4-aminophenyl)[4-(2-( 6-nitrobenzothiazol-2-yl)vinyl)phenyl]amine, 2-[4-((4-(bis(4-aminophenyl)am ino)phenyl)diazenyl)phenyl]-2-phenyl-1, 1-dicyanoethylene, all having high thermal stabilites, were synthesized, characterized, and condensed with hex afluoroisopropylidene diphthalic anhydride or 2-(1,3-dioxoisolounzofuran-5- ylcarbonyloxy)ethyl 1,3-dioxoisobenzofuran-5-carboxylate to yield six high glass transition temperature polyimides (T-g as high as 313 degrees C) for use as poled NLO materials. After casting as thin films, curing, and electr ic field corona poling, these materials exhibit chi((2)) (1064 nm) response s as high as 82.0 pm/V and negligible decay in response upon aging in air a t 100 degrees C for over 1000 h.