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 23 S cm 21 (12 orders higher in magnitude than pure PVDF). The activation energy of the modified nanohybrid membrane is calculated to be 26.9 kJ mol 21 , compared to 10.6 kJ mol 21 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.

New Generation Fuel Cell Membrane Using Swift Heavy Ions

“…Until now, the creation and modification of nanochannels have been focused and their comparative existence in irradiated polymers and their nanohybrids. Nanochannels can be grafted with several polymers e. g. polystyrene, polypyrrole, polyaniline, polythiophene and their derivatives ,,. Further, the grafted species are functionalized through sulfonation enabling the nanochannels for electrical conduction (DC bulk electrical conductivity using two probe methods).…”

“…Further, the grafted species are functionalized through sulfonation enabling the nanochannels for electrical conduction (DC bulk electrical conductivity using two probe methods). Pristine PVDF and its nanohybrid exhibit insulating behavior having the conductivity of the order of 1×10 −15 S cm −1 while polypyrrole (PPy) grafted specimens show the conductivity of PVDF and NH as 3.1×10 −10 and 1.7×10 −8 S cm −1 , respectively (Figure a ) . HCl doped grafted species exhibit higher conductivity by three orders of magnitude up to 10 −5 S cm −1 .…”

“…The activation energy ( E a ) has been calculated from the slopes of the fitted curves using Arrhenius equation. Very high activation energy of 26.9 kJ mol −1 corresponding to the functionalized nanohybrid (NH‐g‐s) indicate the greater thermal stability of electrical conduction at high temperature as opposed to the relatively lower E a value of functionalized PVDF (PVDF‐g‐s) (12.8 kJ mol −1 ) . This is to mention that the activation energy ( E a ) of conduction is governed by the Grotthuss type mechanism and unirradiated PVDF shows the activation energy of 10.6 kJ mol −1[179] and follow almost linear relationship of the conductivity as a function of temperature (inset of Figure b ) .…”

“…On the other hand, NH‐g, NH‐g‐d (doped) and NH‐g‐s exhibit higher current and achieved 21, 42 and 46 nA at 10 V of bias voltage, respectively, indicating greater conduction of grafted and sulfonated nanohybrid as parity with two probe conductivity results. The nanochannels form the typical hetero‐junctions through conducting‐insulator intersections at the walls of the nanochannels is primarily responsible for the greater slope as opposed to the insulating behavior of unirradiated and untreated PVDF and NH showing no change in the I−V characteristics …”

“… Electrical dc conductivity measurements of a) pure, graft, graft‐doped and graft‐sulfonation samples of PVDF and NH; b) Comparison of electrical conductivity as a function of temperature (1000/ T ) of functionalized PVDF and NH samples (the inset figure shows the behavior of unirradiated PVDF and NH); c) I−V plots for the hetero junctions of unirradiated NH and irradiated NH‐g, NH‐g‐d, NH‐g‐s, irradiated with fluence 1×10 10 ions cm −2 …”