Interfacial aggregation states and molecular motion of poly(methylmethacrjlate) with water

Aggregation states and molecular motion of poly(methyl methacrylate) (PMMA) at the interface with water were studied. Neutron reflectivity revealed that the interface between polymer and water was broader than that between polymer and air. This seems to infer that chains at the outermost layer of the film dissolve into the water phase. Also, there existed a swollen layer with the thickness of about 14 nm beneath the interface. Molecular motion at the surface of the PMMA film was activated in comparison with that in the bulk, although relaxation processes were essentially the same in the two. However, an extra relaxation process appeared at the surface of the film under the presence of water. This was assigned to a segmental motion plasticized by sorbed water molecules.