Cellular Automata Modelling of Photo-Induced Oxidation Processes in Molecularly Doped Polymers

David Goldie

doi:10.3390/coatings6040055

Abstract

The possibility of employing cellular automata (CA) to model photo-induced oxidation processes in molecularly doped polymers is explored. It is demonstrated that the oxidation dynamics generated using CA models exhibit stretched-exponential behavior. This dynamical characteristic is in general agreement with an alternative analysis conducted using standard rate equations provided the molecular doping levels are sufficiently low to prohibit the presence of safe-sites which are impenetrable to dissolved oxygen. The CA models therefore offer the advantage of exploring the effect of dopant agglomeration which is difficult to assess from standard rate equation solutions. The influence of UV-induced bleaching or darkening upon the resulting oxidation dynamics may also be easily incorporated into the CA models and these optical effects are investigated for various photo-oxidation product scenarios. Output from the CA models is evaluated for experimental photo-oxidation data obtained from a series of hydrazone-doped polymers.

Highlights

Active thin plastic films are becoming increasingly important in a diverse range of consumer electronic products
Simple rate-equation modelling of molecularly doped polymers (MDPs) photo-degradation, in which the detailed photo-absorption profile across the film thickness is replaced by an average value (G), and all dopant locations are considered to be accessible to oxygen to permit photo-product conversion (Γ = 1), yields exact (γ = 1) exponential dynamics for P(t)
A similar cellular approach has been investigated to evaluate MDP photo-degradation dynamics using simple photo-product conversion rules. The output from such cellular automata (CA) models [6] are evaluated to consider how the Γ and γ parameters in Equation (1) are likely to be influenced under realistic MDP doping and photo-absorption conditions

Summary

Introduction

Active thin plastic films are becoming increasingly important in a diverse range of consumer electronic products. Simple rate-equation modelling of MDP photo-degradation, in which the detailed photo-absorption profile across the film thickness is replaced by an average value (G), and all dopant locations are considered to be accessible to oxygen to permit photo-product conversion (Γ = 1), yields exact (γ = 1) exponential dynamics for P(t). These simplifying assumptions are only likely to apply to weakly-doped (cM small) MDPs, where photo-absorption across the film thickness is weak and significant agglomeration of molecules is unlikely. The output from such cellular automata (CA) models [6] are evaluated to consider how the Γ and γ parameters in Equation (1) are likely to be influenced under realistic MDP doping and photo-absorption conditions

Materials and Methods

Section 3.1. It is now fromthe thediscussions discussions concerning concerning the the CA

Effect

Findings

Discussion