Preparation and characterization of polyelectrolyte complex membranes bearing alkyl side chains for the pervaporation dehydration of alcohols

Quaternized poly(4-vinylpyridine) (QP4VP) with varying side chains tethered to the pyridinium rings was synthesized. An ionic complexation between QP4VP and sodium carboxymethyl cellulose (CMCNa) was performed to prepare their soluble polyelectrolyte complexes (PECs). The structures of QP4VP, QP4VP–CMCNa PECs and PEC membranes (PECMs) were characterized by Fourier transform-infrared spectroscopy (FT-IR), 1H NMR, scanning electron microscope (SEM) and contact angle (CA) measurements. The effects of the side chain length on the surface hydrophilicity, degree of swelling, and sorption selectivity of the PECMs were studied. PECMs were applied to the pervaporation dehydration of aqueous ethanol, isopropanol and n-butanol. It was found that the separation performance could be tailored with the side chain length of the QP4VP, affording a new strategy for the optimization of the separation performance. For example, the flux of PECMs in the dehydration of 10 wt% water–isopropanol at 60 °C increased from 1000 g/m2 h to 1500 g/m2 h, without sacrificing the selectivity, by increasing the side chain length from 0 to 6 carbon atoms.