Phase stability of guest/host photorefractive polymers studied by light scattering experiments

In recent years, we developed plasticized guest-host photorefractive polymers with a glass transition temperature below room temperature.1 However, in these guest/host polymers a gradual crystallization of the chromophores (50% wt.) limits the shelf lifetime of the samples. The lifetime of DMNPAA(2,5-dimethyl-4-(p-nitrophenylazo) anisole) : PVK(poly-vinylcarbazole) : ECZ(N-ethylcarbazole) : TNF(tri-nitrofluorenone) samples with 50% wt. of DMNPAA was found to vary between a few hours and a few months depending on the starting materials and the processing conditions. Here we present a new guest/host photorefractive composite based on isomeric mixtures of the chromophore NPADVBB (4-(4’-nitrophenylazo)l,3-di[(3”or 4”-vinyl)benzyloxy] benzene). These composites exhibit a performance level that is identical to that of DMNPAA-based samples but have an estimated shelf lifetime of several years at room temperature.