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

The surface wettability\nof polymers can be controlled by van der\nWaals interactions, which include induction, orientation, and dispersion\nforces. For most fluoropolymers, the effect of orientation interactions\nis markedly smaller than the others, particularly in structures with\nantiparallel packing, where permanent dipoles may cancel each other\nout. However, poly(vinylidene fluoride) (PVDF), a semicrystalline\npolymer, exhibits unique piezoelectric properties when its polar β-form\ncrystals are oriented via poling treatment. This study investigates\nhow such orientation influences surface wettability. We demonstrate\nthat the wettability of uniaxially oriented PVDF films changes with\npoling treatment. Using sum frequency generation spectroscopy and\ngrazing incidence X-ray diffraction measurements, we found that the <i>b</i>-axis of the β-form crystals near the surface aligns\nperpendicular to the surface under sufficient electric field strength.\nThis alignment facilitates a transition in wettability, which is discussed\nin terms of dipole interactions near the surface. Our findings contribute\nto a deeper understanding of the interplay between molecular orientation\nand surface properties in semicrystalline polymers.