The design and synthesis of high temperature chromophores for use in nonlinear optics and their incorporation into high thermal stability polyimides

A general, convergent approach to the synthesis of a series of stilbene- (via Heck coupling) and azo- (via Mills coupling) based donor-acceptor, second-order nonlinear optical (NLO) chromophores is reported. The synthetic strategy allows the preparation of both acid- and base-reactive structures, yielding diamine functionalized chromophores for incorporation into polyimide backbones. Also presented is a simple method for the oxidation of electron-deficient phenyl hydroxylamines to the corresponding nitroso compounds in homogeneous media using tert-butyl hypochlorite. This oxidative procedure provides the aromatic nitroso compounds in high yields, even with substrates that produce the corresponding azoxy derivatives as byproducts under standard heterogeneous oxidation conditions.; Using this new synthetic method and synthetic strategy, three chromophores, bis(4-aminophenyl)[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)amino)phenyl)diazenyl)phenyl]-2-phenyl-1,1-dicyano$$eth$$yl$$ene, having high thermal stabilites, were synthesized, characterized, and coupled with hexafluoroisopropylidene diphthalic anhydride (6FDA) or the ethylene glycol ester of trimellitic anhydride (TMEG-DA) to yield six high glass transition temperature polyimides (T_g as high as 313°C for use as poled NLO materials. After casting as thin films, curing, and electric field corona poling, these materials exhibit d₃₃ (1064 nm) responses as high as 41 pm/V and exhibit negligible decay in second-order response upon aging in air at 100°C for over 1000 hours.