Permeation of solutes with different molecular size and hydrophobicity through the poly(vinyl alcohol)-graft- N-isopropylacrylamide copolymer membrane

Abstract

Thermosensitive copolymers were synthesized by graft copolymerization of N-isopropylacrylamide on poly(vinyl alcohol) (PVA-g-NIPAAm) and the copolymer membranes were prepared by evaporating solvent from their Me 2SO solution. The swelling ratio of the membrane in water increased gradually with decreasing temperature below 40°C and a considerable increase in the swelling was found below the LCST (33°C). The permeation rate of solutes through the PVA-g-NIPAAm membrane could be controlled by changing temperature. Polyethylene glycols (PEGs) with different molecular weight (400–6000) could be separated by changing temperature from 34 to 45°C. The permeation of butyl alcohols with different hydrophobicity through the slightly swollen membranes above the LCST was found to depend on not only the molecular size but also the hydrophobicity of solutes.