Results are presented on the synthesis and characterization of epoxy-functionalized poly(butyl acrylate-co-methyl methacrylate) latex dispersions. Two pairs of latex dispersions, of low and high molecular weights, were prepared by semicontinuous emulsion polymerization. In each pair, one latex was labeled with phenanthrene, a donor for nonradiative energy-transfer (ET) experiments, and the other was labeled with anthracene, the acceptor. Films were prepared from 1:1 mixtures of donor- and acceptor-labeled latex, and ET experiments were used to study the rate and extent of polymer diffusion in these films. A complicating feature of these experiments was that, even in the absence of an externally added crosslinking agent, the films began to gel as soon as they were formed. The rate of gel formation increased with increasing temperature but never reached 100% under the conditions of these experiments. The presence of a gel fraction caused the rate of polymer diffusion to slow down. An important parameter affecting the rate of diffusion is the amount of time the films are held at relatively low temperatures (4 and 25 degreesC) before being annealed.