| 초록 |
Glass transition temperatures (Tg) of thin poly(styrene-co-methyl methacrylate) and poly(2-vinyl pyridine-co-styrene) films coated on a native oxide Si wafer (100) were measured by ellipsometry and X-ray reflectivity. One component in thin random copolymer films has a weakly favorable interaction between the substrate and thin film, and the other one has a strongly favorable interaction. It was found that the surface and interface have a strong influence on the Tg of thin film coated on substrate: the surface has the effect of reducing Tg, whereas the interface increases the Tg according to the degree of interaction between the substrate and thin film. This degree of interaction can be interpreted as an interaction parameter (k), and is dependent on the composition of random copolymers. We proposed an equation (1/kran=w1/k1+w2/k2) for thin random copolymer films, which relates to the interaction parameter of each component. Various methods were applied in order to estimate the composition and thickness dependence of the Tg (t, w1), and a new equation was obtained based upon a continuous multi-layer model. |
