Fast roll-to-roll fabrication of ultrathin silicon oxide/PDMS membrane on PTFE substrate via interfacial plasma crosslinking

Abstract

Organic solvent nanofiltration (OSN) membranes offer a promising alternative to the conventional separation technology. A plasma-enhanced chemical vapor deposition (PECVD) of hexamethyldisiloxane (HMDSO) was used to introduce ultrathin silicon oxide layer onto the surface of crosslinked polydimethylsiloxane (PDMS) layer. Based on FTIR analysis and XPS depth profiling, the membrane had a 20 nm silicon oxide layer formed on a rubber-like PDMS layer. The membrane showed very hydrophobic characteristics that remained stable for more than two months. A large area silicon oxide/PDMS membrane of 600 cm² could be prepared by the plasma exposure of a few seconds using flexible, non-woven PTFE substrate. The membrane was resistant to organic solvents such as alkanes, alcohols, and aromatic solvents, and did not show pressure-induced compaction at least up to 3 bar feed pressure. The permeance properties of non-polar solvents obey the Hagen-Poiseuille equation for pressure and viscosity. A membrane with a thickness of 180 nm showed a hexane permeance of 34 L m⁻² h⁻¹ bar⁻¹ at a pressure of 0.5 bar and a molecular weight cut-off (MWCO) of 700 Da. The plasma-assisted interfacial polymerization process introduced here provides a fast, continuous way to fabricate advanced OSN membranes, facilitating the widespread implementation of OSN-based separation technologies in various chemical sectors.