Study on the Optimization of Cationic Ring Opening Polymerization of Silicone-Based Epoxy Monomers for Holographic Photopolymers

This study examined the optimum compositions of binder, photo-acid generator (PAG) and sensitizer for the cationic ring opening polymerization of 1,3-bis[2-(3-7-oxabicyclo-[4.1.0]heptyl)]-tetramethyldisiloxane in the presence of polydimethylsiloxane with four epoxide moieties as a co-monomer. When diffractive efficiency (DE) values were compared quantitatively to analyze the effect of the binder on holographic photopolymerization, DE was affected by the viscosity of the binders and miscibility with the monomer mixture. Extremely low DE values were observed when the immiscible dimethyl silicone was used as a binder. Therefore, methylphenyl silicone, which is miscible with the monomer mixture, was used as the binder for further studies. The optimal conditions were a binder viscosity between 250 to 390 cP, and contents of the binder, PAG, and sensitizer were 75–125 wt%, > 6 wt% and 0.05 wt% to the total monomer mixture, respectively.