Employing Glycerol for Improving Diffraction Efficiency, Photosensitivity and Pressure Sensitivity in Holographic Recording Layers

The aim of this review is to explore the improvement in diffraction efficiency, photosensitivity and pressure sensitivity in holographic materials containing glycerol. Glycerol is a well-known, non-toxic, water-soluble polyol compound. Glycerol polymers have attracted increased attention recently due to the diversity of the available compositions. Glycerol provides access to a range of monomers for subsequent polymerizations. Various glycerol containing polymers, including polyvinyl alcohol films, polyesters, polyethers and polycarbonates, have been investigated for different applications. It was discovered in 2009 that the addition of glycerol to the composition of water-soluble holographic photopolymers facilitates the faster formation of holograms due to greater photosensitivity. It was also discovered that the presence of glycerol in holographic photopolymers makes them highly pressure-sensitive. A new family of holographic photopolymer materials, containing glycerol and capable of recording holograms with bright reflections, was reported. The novel photopolymers are composed of glycerol, a polymeric binder, a crosslinking monomer, an initiation system, and sensitising dyes. No wet-processing of holograms is necessary. Each holographic photopolymer film contains bis-acrylamide (BA) monomer in polyvinyl alcohol matrix, triethanolamine and methylene blue dye solution, glycerol and water. It was shown that the new holographic material is capable of reaching a refractive index modulation matching that of the well-known acrylamide photopolymer material, but more quickly. The new holographic photopolymer materials are cheap and environmentally friendly. The use of glycerol to improve diffraction efficiency, photosensitivity and pressure sensitivity in holographic recording layers continues to expand. This review describes the development and applications of glycerol-containing photopolymer materials. An environmentally friendly diacetone-based photopolymer was developed. The positive effect of glycerol on N-vinylpyrrolidone photopolymer was investigated. Finally, potential opportunities for future research in the area of glycerol-containing photopolymers are outlined.