Dehydration of binary methyl acetate–water mixtures under neutral, acidic, and basic conditions was carried out by using PERVAP composite membranes based on polyvinyl alcohol and poly(1-vinylpyrrolidone- co -2-(dimethylamino)ethyl methacrylate) P(VP- co -DMAEMA). The effects of an acid (HCl) and a base (NaOH) on the separation performance of the membrane during the pervaporation process were investigated. The pH-responsive nature of membranes has been confirmed by swelling tests and analysis of the chemical structure of polymeric membranes. In addition, a mechanism of ring-opening of VP units is proposed and correlated to the changes of membrane separation performance.

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Tailor‐made poly(N‐vinylpyrrolidone‐co‐(2‐[dimethylamino]ethyl methacrylate)) P(NVP‐co‐DMAEMA) and poly(N‐vinylpyrrolidone‐co‐N‐vinylimidazole) P(NVP‐co‐PNVIm) with defined monomer molar ratio are synthesized via free radical polymerization. The random copolymers are fully characterized and then blended with polyvinyl alcohol (PVA) to investigate their chemical and thermal properties as membrane materials. Composite membranes are further prepared from the PVA/copolymer blends on a porous support, which are evaluated in terms of separation performance for the dehydration of ethanol by pervaporation. The membranes prepared from the blends exhibit up to four times higher water permeances than pristine PVA membrane, albeit the selectivity is slightly lower. Nevertheless, the membranes from blends with a ratio of 95:5 (PVA/copolymer) show improved selectivity and higher permeance values compared to the commercial PERVAP™ 4155–80, especially the blends composed by the copolymers of coPDMAEMA60 and coPDMAEMA20. The membrane prepared from the blend containing the homopolymer coPDMAEMA100 exhibits the highest water/ethanol selectivity and shows stable separation performance throughout the whole long‐term stability test. Thus, this study demonstrated that by synthesizing tailored copolymers (rather using the commercial ones) and blending with PVA, the separation performance of membranes can be significantly improved and tuned for specific dehydration processes.

Tailor‐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.