Thermo-Responsive Ultrafiltration Block Copolymer Membranes Based on Polystyrene-block-poly(diethyl acrylamide)

Abstract

Within the present work, a thermo-responsive ultrafiltration membrane ismanufactured based on a polystyrene-block-poly(diethyl acrylamide) blockcopolymer (BCP). The poly(diethyl acrylamide) block segment features a lowercritical solution temperature (LCST) in water, similar to the well-knownpoly(N-isopropylacrylamide), but having increased biocompatibility andwithout exhibiting a hysteresis of the thermally induced switching behavior.The BCP is synthesized via sequential “living” anionic polymerizationprotocols and analyzed by1H-NMR spectroscopy, size exclusionchromatography, and differential scanning calorimetry. The resultingmorphology in the bulk state is investigated by transmission electronmicroscopy (TEM) and small-angle X-ray scattering (SAXS) revealing theintended hexagonal cylindrical morphology. The BCPs form micelles in abinary mixture of tetrahydrofuran and dimethylformamide, where BCPcomposition and solvent affinities are discussed in light of the expectedstructure of these micelles and the resulting BCP membrane formation. Themembranes are manufactured using the non-solvent induced phaseseparation (NIPS) process and are characterized via scanning electronmicroscopy (SEM) and water permeation measurements. The latter arecarried out at room temperature and at 50°C revealing up to a 23-foldincrease of the permeance, when crossing the LCST of the poly(diethylacrylamide) block segment in water.