Determination of diffusion rates in acrylamide-based photopolymer material

Holographic data storage systems, utilising photopolymer material as the recording medium, have recently been presented. Because of their relatively low cost and ease of use, due to their self-processing nature, photopolymers provide many potential advantages as the holographic recording material and data storage medium of choice. Photopolymers show promise, for example, for Write-Once Read-Many (WORM) storage systems. The photopolymer recording medium used in this study is an Acrylamide/Polyvinylalcohol (A/PVA) based dry layer. An important material characteristic, which determines the performance of any photopolymer medium, is the spatial frequency response of that material. Previously, applying our Non-local Photo-Polymerisation Driven Diffusion Model, (NPDD), we have discussed the effects on material behaviour of the length of the polymer chains and the rates of diffusion within the material. These parameters have been shown to be critically important in determining the response of the material. If the average length of the Polyacrylamide (photopolymerised Acrylamide monomer, PA), chains is shortened, an increase in the diffusion coefficient of these molecules might be observed. According to the NPDD shorter PA chains should then result in an increase in the materials spatial frequency response, and ultimately in an increase in holographic data storage capacity. In this paper we report on several experiments carried out (a) to determine the diffusion constant of the PA and (b) to also determine the diffusion constants of both water and Propanol in our material layers.