Effect of Surface Molecular Aggregation State and Surface Molecular Motion on Wetting Behavior of Water on Poly(fluoroalkyl methacrylate) Thin Films

The effect of surface molecular motion on the wetting behavior of water on the thin film surfaces of poly(fluoroalkyl methacrylate)s with various fluoroalkyl (Rf) groups [PFMA-C y ; y: fluoromethylene number in Rf groups, y = 1, 2, 4, 6, and 8] was characterized. The receding contact angle of PFMA-C y with short Rf groups (y = 1, 2, 4, and 6) was larger than that of poly(fluoroalkyl acrylate) with short Rf groups [PFA-C y , y ≤ 6]. This stable hydrophobicity observed for PFMA-C y is due to the restriction of thermal molecular motion by the α-methyl group. Wide-angle X-ray diffraction (WAXD) and grazing incidence WAXD measurements revealed that the Rf groups [PFMA-C y , y ≤ 6] were not crystallized. PFMA-C8 showed high advancing and receding contact angles due to the crystallization of fluoroalkyl groups at the surface region. The hydrophobicity of PFMA-C8 was improved after annealing due to the ordering of fluoroalkyl groups.