Design, synthesis, fabrication and application of low Tg three-component photorefractive polymer composites

Low glass transition temperature (Tg) polymer composites, as a new kind of photorefractive (PR) materials, have drawn great attention during the past few years. Their extreme photorefractive performance have been proven to be mainly contributed from the orientational birefringence effect. Usually, to lower the Tg of the composite, a plasticizer had to be added to the photorefractive polymer composite consisting of photoconductive matrix, photosensitizer and nonlinear optical chromophore. Such a four-component composite may suffer deterioration due to crystallization and phase separation. This will induce a low PR performance because only a low concentration of the NLO chromophore can be doped for avoiding the poor stability. To improve the stability and PR performance, a promising design direction that has proven efficient is that the NLO chromophore serves as a plasticizer simultaneously. Recently our attention was paid to develop three-component low Tg composites without a separate plasticizer. We believe that a longer alkoxy chain attached to the azo dye can lower the Tg of the composite. However, the reorienting efficiency as well as the orientational anisotropy may be decreased if the length of the alkoxy chain is too long. Thus there should be an optimized selection for excellent PR performance. Based on such a viewpoint, employing the azo dye DMNPAA we have made an optimization of three-component composites. We developed also a non-azo fast three-component PR composite that worked at short wavelengths. Applications in image storage and phase-distorted image correction were also demonstrated.