Surface and Interfacial Tension of Graft Polymer Melts

Understanding the surface properties of polymer melts is crucial for design of new polymeric coatings, adhesives and composites. Here, we study the effect of chain-end fraction (defined as a ratio of the number of chain ends to the total number of monomers) on the surface and interfacial tension of melts of graft and linear polymers by computer simulations. In our simulations, a film of melt of graft polymers and a film of melt of linear chains with the same total number of monomers are put in contact. By varying the degree of polymerization of the side chains n_sc and their grafting density 1/n_g on the graft polymer backbone, we change the chain-end fraction of graft polymers while keeping the total number of monomers unchanged. The surface tension of the graft polymer melts γ_G and the interfacial tension of the interface between graft and linear polymer melts γ_GL are obtained by using the Bakker’s formula. The simulations show that the surface tension γ_G decreases linearly with increasing chain-end fraction in accordance with theoretical predictions. The interfacial tension γ_GL first decreases then saturates with increasing chain-end fraction.