(179c) Understanding Latex Binder/Water Interfaces Using Atomistic Simulaitons

The stability and rheology of waterborne coatings are results of the interactions of the binders, rheology modifiers as well as other additives such as surfactants. To describe the interfacial properties of binder/water interface, a slab of random copolymer of butyl acrylate and methyl methacrylate in water was simulated using atomistic molecular dynamics simulations. Density profiles of polymer and that of water were calculated to fitted in to the hyperbolic tangent function and the interfacial width was calculated to be ~ 0.4nm. Carbonyl groups at the interfacial region of the polymer slab were found to prefer to form smaller angles with the interface normal to assist the formation of hydrogen bonds. The interfacial tension of the latex/water interface was found to decrease with the increase of the temperature. To validate the accuracy of the model, Interfacial tension of poly butyl acrylate was also calculated and found to agree well with the experimental data (within 10%) at various temperatures.  OPLS and CHARMM force fields were used for all the simulations, and their predications of the interfacial properties of the system are similar.  A coarse grained model based on MARTINI of the latex/water interface was also built and validated against the atomistic simulations.