Nanochannel conduction in piezoelectric polymeric membrane using swift heavy ions and nanoclay

Abstract

A poly(vinylidene fluoride) nanohybrid membrane has been prepared using high energy swift heavy ions (SHI) followed by chemical functionalization. Through-channels were generated by selective etching of the amorphous latent track created during irradiation of SHI, whose average dimensions are varied from 52 nm in pure PVDF to 40 nm for the nanohybrid in the presence of nanoclay, indicating suitable membrane formation using the nanohybrid, as compared to pure PVDF. The nanochannels were suitably grafted with conducting polymer (pyrrole) using the active free radicals caused by SHI irradiation. Spectroscopic and gel permeation chromatographic experiments have been performed to understand the effect of irradiation on filled polymer and subsequent functionalization. Doping and sulphonation on the grafted species has been done to introduce a variety of functionalities. The effect of fluence on the channel width and functionalization study indicates a larger diameter of the channels and formation of a greater ionomer at higher fluence, leading to enhancement of the bulk electrical conductivity up to 10⁻³ S cm⁻¹ (12 orders higher in magnitude than pure PVDF). The activation energy of the modified nanohybrid membrane is calculated to be 26.9 kJ mol⁻¹, compared to 10.6 kJ mol⁻¹ of pure PVDF, indicating superior stability of the nanohybrid membrane at higher temperature as compared to pure PVDF or functionalized PVDF under similar conditions. The nanohybrid conducting membrane produces a current of 46 nA compared to a value of almost zero for pristine PVDF or NH measured through I–V characteristic curves against a bias voltage of 10 V, making the nanohybrid suitable for electrochemical applications.