Diffusion rates in non-local photopolymer materials

In recent years developments in holographic materials have lead to an increasing interest in many areas such as data storage and metrology. Materials such as Acrylamide-based photopolymers are good holographic recording materials, as they are inexpensive and self-processing. The diffusion rate of monomer and the molecular weight of polymerised monomer determine many material characteristics. The length (size) of the polymer chains has a direct effect on the diffusion rate of the polymer and shortening the chain length leads to an increase in the diffusion rate. Shorter chains also decrease the non-local material response parameter and, in consequence, lead to an increase in the spatial frequency response of the material. Thus it is expected that by controlling the polymer chain length (molecular weight) one might control the material spatial frequency response. In this paper we look at the effect of varying the quantity of crosslinking agents on the material and its impact on the rate of diffusion. We then look at determining the rate of diffusion of water within the material to provide a lower limit to the maximum rate of monomer diffusion.