Molecular View of Polymer/Water Interfaces in LatexPaint.

To obtain a molecular level viewof the interface of a latex particlewith water solvent, atomistic simulations using two different forcefields were performed for a slab of methyl methacrylate (MMA)/n-butyl acrylate (BA) random copolymer in water. The carbonylgroups at the polymer/water interface were found to orient significantlytoward the water phase. We calculated the copolymer/water and thecopolymer/vacuum interfacial tensions, and predict a contact anglefor water on copolymer of 77°, consistent with experimental values.We also calculated bulk densities of MMA/BA copolymer, and PMMA andPBA homopolymers, which compare well with experiment, and the structurefactor for PMMA, which agrees with neutron scattering results. Thesimulated Tgof PMMA is not far from itsexperimental value, despite the much shorter chains and faster coolingrates of simulations versus experiments, because these two effectstend to cancel each other. When we correct for these effects, thepredicted Tgis within 5 K of the experimentalvalue. [ABSTRACT FROM AUTHOR]