Phase Separation and Polymer Diffusion in Poly(vinyl acetate−butyl acrylate) Latex Films Prepared by Batch Miniemulsion Polymerization

Abstract

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 °C, 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 °C but became significant at temperatures above 60 °C, suggesting that the BA-rich domains were trapped as occlusions dispersed in a PVAc-rich continuous phase.