Stimuli responsive conductive polyaniline membrane: In-filtration electrical tuneability of flux and MWCO

The membrane performance of conductive polyaniline membrane may be tuned in-situ by applying an external electrical potential. In this study, we focused on the electrical tuneability of polyaniline (PANI) membrane in response to the externally applied potential and also proposed a hypothesis for electrical tuneability in PANI membranes under applied potential. PANI was synthesised via chemical oxidative polymerisation at different polymerisation temperatures (Tpoly) (5 °C, 15 °C and 25 °C) and flat sheet PANI membranes were prepared via non-solvent induced phase separation (NIPS). The influence of electrical tuneability on flux and molecular weight cut-off (MWCO) under external potential during cross-flow filtration was studied. The membrane flux and MWCO were measured for neutrally charged polyethylene glycol (PEG) feed solutions as a function of the applied potential from 0 to 30 V.

The results demonstrated that the electrically conductive PANI membranes showed a decrease in permeance and MWCO under the applied potential in the cross-flow filtrations, with a higher applied potential producing to a larger decrease. The PANI membrane (Tpoly = 15 °C) showing the greatest MWCO decrease (down to 2800 g mol−1) at 30 V from 6000 g mol−1 at 0 V. It was hypothesised that the swelling of polymer chains caused the narrowing of pore size of membranes on the application of high external potential and resulted in reduction of membrane flux and MWCO. Overall these results suggest that the electrically conductive PANI membranes can self-regulatively adjust their separation properties in response to electrical stimuli, allowing control over neutrally charged molecules transport beyond the ion based separations under applied potential.