Measuring chain diffusion coefficients and activation energy during coalescence of fluorescence-labeled hard latex particles

The steady-state fluorescence (SSF) technique was used to study interdiffusion of polymer chains across the particle–particle junction during film formation from hard latex particles. The latex films were prepared from pyrene (P) and naphthalene (N) labeled poly(methyl methacrylate) (PMMA) particles and annealed for long time intervals above the glass transition temperature (T_g) between 170 and 220°C. A novel correction method was suggested and employed to eliminate changing of the optical density of latex films after such annealing processes. P and N fluorescence intensities solely from the energy-transfer processes were monitored versus annealing time and were used to measure the polymer chain diffusion coefficients D_p and D_N, which were found to be between 4.34 × 10^–14 and 7.68 × 10^–13 cm²/s for an annealing temperature between 170 and 220°C. Using these diffusion coefficients with the Arrhenius relation, the diffusion activation energy for the polymer backbone was found to be 28 kcal/mol.