Endowing piezoelectric and anti-fouling properties by directly poling β-phase PVDF membranes with green diluents

Membrane fouling can be efficiently mitigated by the vibration of the piezoelectric membrane stimulated by AC signals, but it is still a challenge to fabricate piezoelectric membranes with great efficiency, low energy-consumption, and no harm to the environment during its preparation. The present work provides a new approach to poly(vinylidene fluoride) (PVDF) membranes with piezoelectric properties by directly poling β-phase PVDF membranes using green diluents, which revealed better piezoelectric properties than poling α-phase PVDF membranes. Basically, absolute β-phase crystals of PVDF membranes were induced over thermally induced phase separation with the addition of Acetyl tributyl citrate (ATBC)/ionic liquid ([BMIM]PF6), which are regarded as green and environment-friendly diluents. To endow the piezoelectric property to the β-phase PVDF membrane, a poling process was necessarily conducted. The effect of the poling process on the membrane structure, morphologies, properties, and performances was investigated. Meanwhile, a vibration test for both of the poled and unpoled membranes was performed in an excitation of the alternating signal. The results demonstrated that the poling process positively endowed the piezoelectric property to the PVDF membranes. The membrane structure, morphologies, and performances of the membranes were also changed to some extent by the poling process. Additionally, filtrations of the poled membrane both with and without electrical signals were carried out to test their antifouling performance on the CaCO3 suspension system and BSA solution, respectively. It was observed that the stable flux of the membranes notably improved when subjected to an electrical AC signal. Thus, it depicted that the piezoelectric PVDF membrane directly poled from the β-phase possesses a promising antifouling performance due to its high piezoelectric vibration.