Packing Effect on Latex Film Dissolution: A UV-Visible Study

Latex films with various thicknesses are formed from pyrene (P) labeled poly (methyl methacrylate) (PMMA) latex particles sterically stabilized by poly isobutylene (PIB). Annealings of latex films were performed above T(g) at elevated temperatures up to 270 degrees C for 30 min time intervals. The UV-Visible (UVV) technique was used for monitoring latex film formation and dissolution. It was observed that thicker films formed more transparent films than thinner films. Absorption of solvent molecules (chloroform) into the annealed latex film was followed by diffusion of PMMA chains into a solvent reservoir. Diffusion of pyrene-labeled PMMA chains was monitored in real time by the absorbance change of pyrene in the polymer-solvent mixture. A diffusion model with a moving boundary was employed to quantify real-time UVV data. Diffusion coefficients of PMMA chains were measured and found to be between 2.6 x 10(-9) and 9.7 x 10(-13) cm(2) s(-1) for the latex films in various thicknesses. It is observed that thicker and more transparent films dissolved much faster than the thinner and turbid films; i.e., highly packed films dissolve more easily. Copyright 1999 Academic Press.