Dehydration performance of double-network poly(vinyl alcohol) nanocomposite membranes (PVAs-DN)

Double-network poly(vinyl alcohol) nanocomposite membranes (PVAs-DN) were prepared from interpenetrating of two PVA networks. The sequential method was employed in which the first PVA network was completely established from crosslinking of high molecular weight PVA (HPVA) in the presence of silica nanospheres (SNSs) prior to a formation of the second network by the thermal crosslinking of low molecular weight PVA (LPVA). SNSs particle loading was varied at 1 and 3.5 wt% which assured an even distribution of the particles in PVAs-DN matrix. Introducing of SNSs enhanced the crystallinity and mechanical properties of PVAs-DN as revealed by XRD and DMA analysis. Furthermore DMA result indicated that HPVA and LPVA networks in PVAs-DN membranes, despite their chemically identical structure, established a separate network and possessed its own relaxation. Effect of temperature on the sorption and the pervaporation was performed using 90 wt% ethanol solution. The results showed that the permeability and the selectivity of water were pronouncedly improved in SNSs-filled PVAs-DN membranes compared with unfilled one and HPVA-SN membranes. Consequently thermodynamic parameters and Arrhenius activation parameters were determined.