The photon transmission technique was used to monitor the evolution of transparency during film formation from nano-sized copolymeric latex particles. The latex films were prepared from poly(methyl methacrylate-co-butyl methacrylate) (P(MMAco-BMA)) particles which were produced by microemulsion polymerization, These films were annealed at elevated temperatures in various time intervals above the glass transition temperature (T-g) of P(MMA-co-BMA). It is observed that the transmitted photon intensity (I,) from these films increased as the annealing temperature increased. There are three different film formation stages, These stages are explained by the void closure, healing, and interdiffusion processes, respectively. The activation energies for viscous flow (DeltaH approximate to 16 kcal/mol), minor chains (DeltaE(H) approximate to 27 kcal/mol), and backbone motion (DeltaE(b) approximate to 132 kcal/mol) were obtained using various models. Void closure (tau (v), T (v)) and healing points (tau (H), T (H)) were determined. Using the time-temperature pairs, void closure and healing activation energies were measured and found to be 21 and 30 kcal/mol, respectively. (C) 2001 Academic Press.