Investigation of polymerization rate in an acrylamide-based photopolymer using Raman spectroscopy

Diffusion models predict that polymerization and diffusion rates are the key factors that control the dynamics and the final properties of a holographic grating recorded in a photopolymerizable material. Diffusion rates during the initial phase of the holographic recording have already been studied and reported. We now report the investigation of the polymerization rate in an acrylamide-based photopolymer using Raman spectroscopy. The polymerization rate constant was estimated by monitoring the intensity of the characteristic Raman peaks at 1284 cm ^-11 corresponding to the bending mode of CH vinyl bond in acrylamide and 1609 cm ^-1 corresponding to the carbon-carbon double bond (C=C) in acrylamide as a function of illumination time. The dependence of the residual monomer concentration on the exposure time was fitted using a mono exponential fitting function. The value of the polymerization constant was estimated to be 0.043 s ^-1(mW/cm ²) ^-0.5 for this formulation. A comparison with some other photopolymer systems reported in the literature reveals that the acrylamide-based photopolymer system is characterized by a relatively fast polymerization rate constant. The results from the present study give significant information for better understanding of the process of holographic recording in acrylamide-based photopolymer system.