Spatial and temporal evolution of the photoinitiation rate for thick polymer systems illuminated with polychromatic light

A complete and accurate description of polychromatic photoinitiation in thick systems is presented in which the incident intensity and molar absorptivities of all components may be independently specified at each incident wavelength. The analysis reveals that the photoinitiation rate profile obtained with polychromatic illumination is considerably different from the sum of the monochromatic profiles, and that synergistic coupling of the contributions from multiple wavelengths can lead to both high rates of initiation near the surface and significant initiation deep in the sample. Simulations reveal that the shape and attributes of the aggregate photoinitiation rate profile may change markedly if any of a number of variables are changed, including the relative intensities, the absolute intensity, initiator concentration, and degree of photobleaching. The polychromatic description of photoinitiation presented here can be applied to any combination of monomer, initiator, and light source and may provide an invaluable tool for design of these systems.