| 초록 |
The structure and properties of the surface of the films have been known to be quite different from those of bulk. However, less work has been reported on the semi-crystalline polymer systems. Here we prepared thin films of a completely miscible polymer blend composed of PVDF and PMMA and the composition, crsytalline microstructure, and mechanical properties of the surface of the blend film are investigated. The chemical composition of the surface characterized by the XPS shows that blend of PVDF and PMMA is miscible in the solid state, even though the surface is enriched with PVDF. Grazing incidence x-ray diffraction (GIXD) and nano indentation have revealed the difference in crystalline structure and mechanical behavior in accordance with PMMA content in the surface region. It was found that the crystallinity index of the surface is higher than that of the bulk. As PMMA content increases, the lamellae of the spherulite are less twisted, which indicates that the (100) plane is oriented parallel to the substrate. Even though we annealed the samples under the same temperature, the incoproration of PMMA depressed the melting temperature of the blend system, and reduced ΔT gave larger spherulite and more perfect orientation. In addition, this difference of crystalline structure also affected mechanical properties of the surface. As PMMA content increases, reduced modulus and hardness increase. This is caused by the higher PMMA content in the interlamellar amorphous region and orientation effect of the lamellae. |
