Interdiffusion vs Cross-Linking Rates in Isobutoxyacrylamide-Containing Latex Coatings

Abstract

We describe the relative rates of polymer diffusion and cross-linking in a latex film containing 2 wt % (1.3 mol %) of N-isobutoxymethylacrylamide (IBMA) as a cross-linking agent. The latex base monomer is a 4:5 weight ratio copolymer of butyl acrylate and methyl methacrylate (BA−MMA) with a glass transition temperature of 12 °C. Polymer diffusion was monitored by direct energy transfer (ET) in films prepared from latex particles labeled with phenanthrene as the donor and anthracene as the acceptor. In a model film without IBMA, the quantum yield for ET (ΦET) increased to its maximum value of 0.62 in a few minutes at 120 °C, whereas at 80 °C the films required hours of annealing to achieve full mixing. The temperature dependence of the diffusion rate indicated an effective activation energy of 43 kcal/mol. In contrast, a film prepared from latex of similar molecular weight containing 2 wt % IBMA formed gel rapidly at 80 °C in the presence of 0.5 wt % toluenesulfonic acid. The system reached its maximum ge...