Interdiffusion at Ring-Shaped Polystyrene / Its Deuterated Counterpart Bilayer Interfaces

Time evolution of interfacial thicknesses between a cyclic polystyrene (c-hPS) / its deuterated counterpart (c-dPS) and a linear polystyrene (l-hPS) / its deuterated counterpart (l-dPS) bilayer films was investigated by neutron reflectivity as a function of molecular weight. The interfacial thickness of (c-hPS/c-dPS) film with molecular weight of 15k was almost equivalent to that of (l-hPS/l-dPS) one at any given annealing time. In contrast, the interfacial thickness of (c-hPS/c-dPS) film with molecular weight of 115k was significantly larger than that of (l-hPS/l-dPS) film at any given annealing time, indicating that the diffusion constant of c-PS ($D_{c})$ is qualitatively larger than that of l-PS ($D_{l})$. It might be explained in terms of less topological constraint of the entanglement for the cyclic PS at high molecular weight region.