The surface chemical composition and structure of a fluorocarbon- hydrocarbon block copolymer

The thermal properties of the fluorocarbon-hydrocarbon copolymer [-(CF ₂)₈-(CH₂)₁₀-]_N were characterized using polarized optical microscopy, differential scanning calorimetry and X-ray diffraction. The results revealed the presence of a crystalline phase and a threaded nematic liquid crystal phase. The changes in the surface composition during annealing were studied in situ using time-of-flight secondary ion mass spectrometry. The spectra were interpreted using principal component analysis (PCA). The surface compositions at different thermal states can be distinguished by PCA. Moreover, a PCA loadings analysis revealed a continuous increase in the concentration of the hydrocarbon segments on the surface as the polymer gradually changed from the amorphous state to the liquid crystal state and finally the crystalline state. This suggests that the chemical composition of the surface in the amorphous state is controlled by the surface energy difference between the fluorocarbon and hydrocarbon segments, while the surface composition in the crystalline state is controlled by the structural ordering of the fluorocarbon segments. The results also showed that the surface re-construction of this polymer was highly reversible.