An understanding of the photochemical and photo-physical processes, which occur during photopolymerization is of extreme importance when attempting to improve a photopolymer material’s performance for a given application. Recent work carried out on the modelling of the mechanisms which occur in photopolymers during- and post-exposure, has led to the development of a tool, which can be used to predict the behaviour of these materials under a wide range of conditions. In this paper, we explore this Non-local Photo-polymerisation Driven Diffusion model, illustrating some of the useful trends, which the model predicts and we analyse their implications on the improvement of photopolymer material performance.

Phenanthrenequinone (PQ) doped poly(methyl methacrylate) (PMMA) photopolymer material has received much attention in the literature. However, further development requires that a more physical material model be developed. In this article, such a model is presented. The model includes: (1) the time-varying photon absorption, including the absorptivity of a second absorber, i.e., the singlet excited state of PQ; (2) the recovery/regeneration and the bleaching of the excited-state PQ; (3) the nonlocal effect; and (4) the diffusion effects of both the ground- and excited-state PQ molecules and of the methyl methacrylate (MMA). A set of rate equations are derived, governing the temporal and spatial variations of each chemical component concentration. Compared to previous models presented in the literature in this paper: (1) the second absorber is included; (2) the diffusion of all the PQ states is considered; and (3) the first-harmonic refractive index modulation is calculated in a more physically reasonable way. Simulations of the normalized transmission are presented. The effects of the nonlocal material response and the diffusion of both ground-state and excited-state PQ molecules are also examined. The model is applied to analyze experimental results in Part 2 of this paper.