Analysis of PEA photopolymers at zero spatial frequency limit

Abstract

The PEA photopolymer is composed of dipentaerythritol penta/hexa-acrylate as monomer and binder, N-vinyl pirrolidone as crosslinker, ethyl eosin as dye and N-methyl diethanolamine as radical generator. This photopolymer is suitable to work with dispersed liquid crystal molecules in dynamic holographic and diffractive applications. In order to characterize these materials we have analyzed the behaviour of different compositions at zero spatial frequency limit. This method is based on an interferometer that has been successfully applied in the phase-shift versus applied voltage characterization of liquid-crystal displays, in addition to that it has been applied to characterize PVA/AA and PVA/NaAO photopolymers. In PEA case there is no shrinkage since the photopolymer is coverplated. Samples have a glass substrate as the cover plate. In our analysis we have studied the importance of the monomer, crosslinker and crystal liquid molecules concentrations, in the phase shift produced in the layer during photopolymerization process.