Vapor-Phase-Induced Interfacial Interpenetration for High-Performance Polymeric Dehydration Membranes

Polymeric membranes have been applied widely for dehydration, yet their separation efficiency is often limited by the highly swellable nature of solvent-permeable polymer layers, resulting in reduced selectivity. Herein, a membrane with controlled interfacial interpenetration of a highly crosslinked organosiloxane layer and a water-absorbing poly(vinyl alcohol) (PVA) layer is developed, where the organosiloxane polymer is deposited via a solvent-free vapor-phase deposition process. The vapor-phase deposition enables the formation of an ultrathin, conformal top layer that preserves the integrity of the underlying water-swellable PVA while allowing control over interfacial structure. By varying the deposition time of the organosiloxane polymer and the annealing temperature of the underlying PVA substrate, the extent of interfacial interpenetration can be systematically tuned, confirmed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling. Furthermore, in situ spectroscopic ellipsometry verifies the suppressed swelling behavior of PVA layer, suggesting the role of interpenetrated interface. The optimized membrane exhibits a high separation factor of 1310 at a flux of 662 g m -2 h -1 for the pervaporation of an 80/20 wt.% isopropyl alcohol/water mixture, demonstrating the effectiveness of this strategy. This solvent-free, environmentally benign approach achieves high selectivity without compromising flux, providing a rational strategy to advanced dehydration membranes with precisely tailored separation properties. • Vapor-phase infiltration induces robust interfacial interpenetration of polymer. • Interpenetrating extent is tunable via PVA annealing and pV4D4 deposition time. • Engineered interface suppresses swelling kinetics for enhanced size-dependent transport property.