Study of simultaneous dual-sided electrophoretic deposition onto porous polymer membrane

Electrophoretic deposition (EPD) is widely used in both industrial and research applications for surface modification. Nevertheless, applying EPD to insulating substrates is still relatively rare and has mainly been achieved on porous substrates that are directly connected to a conductive electrode. In this work, the EPD mechanism and deposition kinetics of polyelectrolytes, such as polyethylenimine (PEI) and polyacrylic acid (PAA) were investigated, along with the simultaneous dual-sided deposition of lithium titanate-PEI composite coatings on a commercial porous polymer membrane (Celgard 2325). Although the basic dual-sided deposition approach was demonstrated in our earlier work, the present manuscript addresses the coupling and kinetic limitations underlying that process. The central scientific question concerns how the formation of a deposit on one plane of a porous, electrically insulating membrane influences electrophoretic transport and deposition on its opposite plane, when the membrane is spatially separated from and electrically disconnected from both electrodes. Pore blockage and redistribution of the local electric field were found to result in self-limiting deposition behavior proving complex interplay between drift and hindered diffusion within porous networks. Introducing an "opposition" term into the Sarkar-Nicholson and Ferrari-Moreno models enabled accurate fitting of the experimental data and provided a phenomenological description of the progressive restriction of EPD caused by the growing counter-deposit.