Synthesis and characterization of tailor-made N-vinylpyrrolidone copolymers and their blend membranes with polyvinyl alcohol for bioethanol dehydration by pervaporation

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 TM 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.