Molecular dynamics study of the influence of solid interfaces on poly(ethylene oxide) structure and dynamics

Molecular dynamics (MD) simulation studies of the interface between poly(ethylene oxide) (PEO) and TiO2 have been performed at 423 K using a quantum chemistry-based force field. MD simulations revealed that the PEO density is significantly perturbed by TiO2 surfaces, forming layers of highly dense polymer (compared to the bulk melt) that persisted up to 15 A from the surface. Conformational and structural relaxations of the interfacial PEO were found to be dramatically slower than those of bulk PEO. These effects are attributed to an intrinsic slowing down of PEO dynamics and increased dynamic heterogeneity of the interfacial polymer. The surface structure and electrostatic interactions between PEO and TiO2, rather than the increased polymer density at the TiO2 surface, determine the nature of PEO relaxation at the TiO2 interface.