Steady state fluorescence (SSF) in conjunction with Monte Carlo simulations was used to study interdiffusion of polymer chains across the particle-particle junction, during film formation from high-T latex particles. The latex films were prepared from pyrene (P) and naphthalene (N) labelled poly (methyl methacrylate) particles, and annealed in elevated time intervals above the glass transition temperature (T-g) at 180 degrees C. Scanning electron microscopy (SEM) was used to detect the variation in physical appearance annealed latex films. Monte Carlo simulations were performed to model the N and P fluorescence intensities (I-N and I-P) using photon diffusion theory. The number of N and P photons (N-N and N-P), emerging from the front surface of the latex film, are calculated when only N is excited where N-P photons are combined of photons from radiative (N-PR) and non radiative (N-PNR) energy transfer processes. In simulations, annealing time, t, and the mean free path of a photon [r] are assumed to obey the Fickian diffusion model. A novel correction method was suggested, and employed to eliminate the P intensity due to the optical variation in latex film. P intensities from solely the energy transfer processes were monitored vs annealing time, and were used to measure the polymer chain diffusion coefficient (D), which was found to be 5.9 x 10(-13) cm(2) s(-1) 180 degrees C. (C) 1997 Elsevier Science Ltd.