Reaction kinetics and mechanics in photo-polymerised networks

Objectives: The aim of this paper is to address the relationship, existing in photo-cure composites, between the polymer-network forming reactions, along with their kinetics, and the resultant stress-transmitting micro-mechanical behavior. Methods: Photon numbers and energies were calculated and compared for a simple model monomer-composite system. Expressions for tight irradiance at depth within materials were computed and the consequences of steady-state assumptions in kinetic models of conversion and shrinkage-strain rate were considered. Results: The resultant stress-transmitting properties are a complex function of photon-transport, absorption by photo-initiators, possibly non-steady-state free-radical cross-linking, collapse of free-volume and development of an elastic-network displaying non-homogenous structure, viscoelasticity and aging effects. Significance: Researchers need to be aware of the complexity of these systems, so as to adequately control experimental variables and to develop more sophisticated models and hypotheses for experimental validation. (C) 2004 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.