SPECTROSCOPIC STUDIES OF POLYMER INTERDIFFUSION DURING FILM FORMATION

Polymer interdiffusion between latex particles during film formation is studied using the fluorescence technique of nonradiative energy transfer (NET). Model emulsion polymers of poly(butyl methacrylate) and poly(amyl methacrylate), labeled with the energy transfer pair of 1-naphthylethyl methacrylate or 9-anthryl methacrylate, are investigated. The effects of particle size, polymer glass transition temperature, and polymer compatibility on the rate and extent of interparticle diffusion are measured. In addition, the time dependence of transmission electron microscopy images during the final stage of film formation augments the conceptual picture of interdiffusion. A change in particle size is observed to enhance the intermixing rate in proportion to the particle 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 equations, albeit throughout a comparatively narrow temperature range, and the activation energies were found to be equivalent within experimental error for the two acrylates. The extent of polymer interdiffusion in a film formed from a blend of the two methacrylate compositions appears to be affected by the compatibility of the components.