Development of refractive-index change polymers by external stimuli

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Tunable and controllable refractive index of materials is important key technology in today's optical application such as switches, and data storage devices. Due to the increasing demand for such materials, we focused on the refractive index change materials without any release products based on photoreactive functional polymers. We found that the structural change from S-(2-benzoxazolyl) thioester to bezoxazoline-2-thione under heating increase the refractive index due to the production of the polar functional C=S bond. We designed and synthesized new monomers containing two S-(2-benzoxazolyl) thioester groups in order to enhance the change in refractive index. Also, polymers containing salicylideneaniline groups both in the main chain and in the side chain were prepared by the direct condensation reaction of diformyl derivatives with diamino derivatives and by radical polymerization, respectively. The chromism of these polymers was hard to detect due to their amorphous structure.