Poling-Induced Wettability Transition of a Uniaxially Oriented Poly(vinylidene fluoride) Film

The surface wettability of polymers can be controlled by van der Waals interactions, which include induction, orientation, and dispersion forces. For most fluoropolymers, the effect of orientation interactions is markedly smaller than the others, particularly in structures with antiparallel packing, where permanent dipoles may cancel each other out. However, poly(vinylidene fluoride) (PVDF), a semicrystalline polymer, exhibits unique piezoelectric properties when its polar β-form crystals are oriented via poling treatment. This study investigates how such orientation influences surface wettability. We demonstrate that the wettability of uniaxially oriented PVDF films changes with poling treatment. Using sum frequency generation spectroscopy and grazing incidence X-ray diffraction measurements, we found that the b-axis of the β-form crystals near the surface aligns perpendicular to the surface under sufficient electric field strength. This alignment facilitates a transition in wettability, which is discussed in terms of dipole interactions near the surface. Our findings contribute to a deeper understanding of the interplay between molecular orientation and surface properties in semicrystalline polymers.