Self-assembled polyurea macromer nanodispersion and resulting hybrid polyurea-acrylic emulsions and films

摘要

A polyurea macromer (PUM) was synthesized and dispersed in basic conditions to form self-assembled nanoparticles (<20 nm dispersions, up to 30 wt % aq. soln.). These nanoparticles enabled surfactant-free emulsion polymerization to form hybrid polyurea-acrylic particles despite the absence of a measureable water-soluble fraction. The T-g of the starting PUM material was a strong function of the PUM's extent of neutralization and hydration (varying between 100 degrees C and >175 degrees C) due to changes in hydrogen and ionic bonding. Two separate hybrid polyurea-acrylic emulsion systems were prepared: one by direct polymerization of (meth)acrylic monomers in the presence of the nanodispersion and a second by a physical blend of PUM nanodispersion with an acrylic latex control. The direct polymerization method resulted in a hybrid emulsion particle size that developed by a mechanism resembling conventional emulsion polymerization and was unlike that described for seeded polyurethane dispersion systems. Film hardness was shown to increase with increasing coating thickness for the hybrid film prepared by direct polymerization. The resulting mechanical properties could be explained by applying mechanical models for a composite foam structure. These results were unprecedented for normal elastomer films. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1373-1388