Azo-carbazole copolymer-based composite films with high optical transparency for updatable holograms

Abstract

The development of materials with high diffraction efficiency, fast response time, holographic gratings with optical preservation stability, and long-term optical transparency are key for the practical application of updatable holograms. The identification of updatable holograms using photofunctional materials is essential to achieving updatable holography. A holographic composite material based on an azobenzene-functionalized copolymer consisting of 3-[(4-cyanophenyl)azo]-9H-carbazole-9-ethyl acrylate (acrylate monomer with CACzE) with methyl methacrylate (MMA) (poly(CACzE-MMA)) and the azo-carbazole dye 3-[(4-cyanophenyl)azo]-9H-carbazole-9-ethanol (CACzE) has been proposed as a promising candidate for updatable holographic materials. The holographic composite materials are based on the copolymer poly(CACzE-MMA)); azo-carbazole dye CACzE composites were added with plasticizers, and their plasticized composites were evaluated from their Raman-Nath diffraction properties, UV-visible absorption spectra, and haze values. The plasticized composite material that exhibited the most remarkable holographic properties was poly(CACzE-MMA)/CACzE/DPP (45/15/5 wt%), with first-order diffraction efficiency (η₁), response time (τ), retention ratio (R_300s), and haze values of 29.5%, 2.1 s, 94%, and 1.2%, respectively. The holographic stereograms and Lippmann holograms recorded using the poly(CACzE-MMA)/CACzE/DPP (50/15/5 wt%) composite film were reconstructed and were refreshed to their original states by further heat treatment. Accordingly, the poly(CACzE-MMA)/CACzE/DPP (45/15/5 wt%) composite material is expected to make a valuable contribution to the application of updatable holograms.