Amphiphilic Poly(vinyl alcohol) Membranes Leaving Out Chemical Cross‐Linkers: Design, Synthesis, and Function of Tailor‐Made Poly(vinyl alcohol)‐b‐poly(styrene) Copolymers

Abstract

AbstractTailor‐made poly(vinyl alcohol)‐b‐poly(styrene) copolymers (PVA‐b‐PS) for separation membranes are synthesized by the combination of reversible‐deactivation radical polymerization techniques. The special features of these di‐block copolymers are the high molecular weight (>70 kDa), the high PVA content (>80 wt%), and the good film‐forming property. They are soluble only in hot dimethyl sulfoxide, but by the “solvent‐switch” technique, they self‐assemble in aqueous media to form micelles. When the self‐assembled micelles are cast on a porous substrate, thin‐film membranes with higher water permeance than that of PVA homopolymer are obtained. Thus, by using these tailor‐made PVA‐b‐PS copolymers, it is demonstrated that chemical cross‐linkers and acid catalysts can no longer be needed to produce PVA membranes, since the PS nanodomains within the PVA matrix act as cross‐linking points. Lastly, subsequent thermal annealing of the thin film enhances the membrane selectivity due to the improved microphase separation.