SPECTROSCOPIC STUDIES OF POLYMER INTERDIFFUSION DURING FILM FORMATION

Polymer interdiffusion between latex particles during film formation i s studied using the fluorescence technique of nonradiative energy tran sfer (NET). Model emulsion polymers of poly(butyl methacrylate) and po ly(amyl methacrylate), labeled with the energy transfer pair of 1-naph thylethyl methacrylate or 9-anthryl methacrylate, are investigated. Th e effects of particle size, polymer glass transition temperature, and polymer compatibility on the rate and extent of interparticle diffusio n are measured. In addition, the time dependence of transmission elect ron microscopy images during the final stage of film formation augment s the conceptual picture of interdiffusion. A change in particle size is observed to enhance the intermixing rate in proportion to the parti cle surface area to volume ratio, while leaving the apparent diffusion coefficient unchanged. The dependence of the diffusion coefficient on temperature is adequately described by both the WLF and Arrhenius equ ations, albeit throughout a comparatively narrow temperature range, an d the activation energies were found to be equivalent within experimen tal error for the two acrylates. The extent of polymer interdiffusion in a film formed from a blend of the two methacrylate compositions app ears to be affected by the compatibility of the components.