Influence of Electrospinning and pH Conditions on PVDF-HFP Nanofibrous Membranes for Agricultural Soil Applications

Abstract

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) electrospun nanofibrous membranes (ENMs) exhibit outstanding chemical resistance, high surface-to-volume ratio, and polymorphic behavior, where the electroactive β-phase is particularly desirable for functional and environmental technologies. In this work, we evaluate the influence of pH and electrospinning processing parameters on the structural, morphological, and surface properties of PVDF-HFP ENMs for potential agricultural soil applications. Membranes were fabricated under varied electrospinning conditions -adjusting applied voltage, solution feed rate, and tip-to-collector distance- and subsequently exposed to aqueous solutions at pH 2, 4, 6 and 9 for 24 h. Crystallinity and crystalline phase distribution were analyzed via X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), while scanning electron microscopy (SEM) and water contact angle measurements evaluated nanofiber morphology and wettability, respectively. The results demonstrate that the chemical environment significantly affects membrane crystallinity. Notably, treatment at pH 2 yielded a marked enhancement in the relative contribution of the electroactive β-phase, indicating that strongly acidic media promote macromolecular rearrangements that stabilize this phase. Furthermore, the extent of this transformation depends on the initial electrospinning parameters, confirming a synergistic interaction between processing conditions and post-treatment environment. Therefore, controlled acidic exposure emerges as an effective post-processing route for tailoring the polymorphic composition and functional performance of PVDF-HFP ENMs in acidic soil environments.

Keywords: Electrospun nanofibrous membranes; pH; environmental remediation.