| 초록 |
Thin films of various polymers (polyethylene, polypropylene, polyisobutene, poly(alkyl methacrylate)s and polystyrene) on graphite substrates have been studied by molecular dynamics simulations using explicit atom models. The density profiles and order parameters at the solid-liquid interfaces are found to depend much more strongly on the atomic structure of monomer units as compared with liquid-vacuum interfaces. In the solid-liquid interfacial region, the chain axes of various polymers form layer structure with the chain vector oriented parallel to the surface. However, the backbone planes of poly(alkyl methacrylate)s stand up on the substrates as the side branches being supporting legs while those of polyolefins lay down to maximize the adhesion interaction. The orientation autocorrelation functions of the side-chain axes show that the relaxation time of the solid-liquid interface system is shorter than that of the bulk but longer than that of the free standing film. |
