| The photorefractive (PR) effect is being pursued for optical processing applications such as holographic optical data storage, optical computing and switching, and frequency doubling of laser light. Until 1990, only inorganic crystals were found to be photorefractive. During the past few years, organic materials and, more recently, polymers with photorefractive properties have been synthesized. The synthesis of new PR systems is crucial to the advancement of this fast growing field. Polymeric photorefractive materials may be superior to both organic and inorganic systems due to many advantages associated with polymers. Polymers possess good thermal stability, low dielectric constant, and are easy to process. However, in order to achieve the PR effect in a polymer, it is thought that the material must contain photocharge generating (CG) and transporting (CT) functionalities, charge trapping sites, and nonlinear optical (NLO) chromophores.; We report a series of potentially photorefractive polymeric systems (polysiloxanes, polyimides, polyimines, polystyrene, polymethyl methacrylate, and polyurethanes). Almost all of these polymers contain azobenzene or stilbene-based chromophores with different electron-donating and electron-withdrawing groups incorporated to serve as the NLO component. Di- and triphenylamine units were chosen to serve as the charge transporting moiety. These polymers represent a wide range of thermal properties, i.e., Tg and thermal stability. Two approaches to the synthesis of these materials were adopted. In the first approach, the CT and NLO moieties were covalently attached to the polymer backbone as side chains. The second approach, in contrast, incorporates the CT and NLO moieties in the polymer backbone in an alternating fashion. |
