A series of poly(vinyl acetate-butyl acrylate) P(VAc-BA) latex particles, with a 4:1 weight ratio of VAc and BA, unlabeled and labeled with phenanthrene (Phe) as the donor and with 4'(dimethylamino)benzophenone (NBen) as the acceptor, were prepared by batch miniemulsion polymerization in the presence and absence of a chain transfer agent. The latex particles were characterized by a phase-separated morphology, and the dyes appeared to be localized in the BA-rich domains. One set of samples, which we refer to as "gel-free", had a negligible gel content, whereas the gel-containing samples for the energy-transfer studies of polymer diffusion had a gel content of ca. 34%. For gel-free samples, diffusion led to complete mixing of donor- and acceptor-labeled polymer during the drying process, at even 4 degreesC, suggesting that the PBA-rich domains were continuous. For the gel-containing samples, the diffusion rate (for molecules not part of the gel network) was negligible at 22 degreesC but became significant at temperatures above 60 degreesC, suggesting that the BA-rich domains were trapped as occlusions dispersed in a PVAc-rich continuous phase.