Grafting of Poly(2–hydroxyethyl methacrylate) on Natural Rubber (NR–g–PHEMA): Characterizations and Water Sorption Selectivity of NR–g–PHEMA Membranes

Abstract

Poly(2–hydroxyethyl methacrylate) (PHEMA) was grafted onto NR latex particles employing emulsion polymerization technique. Grafting efficiency (%GE) of PHEMA on NR particles was found to increase with increasing 2–hydroxyethyl methacrylate monomer (HEMA). Differently, %GE increased rapidly at low initiator concentrations before leveling off at higher concentrations. The NR–g–PHEMA latex was cast into a thin membranes. The membranes were subjected to the tensile testing. The Young’s modulus of NR–g–PHEMA membrane was found to improved as %GE increased in contrast to the elongation at break. Revealing by DSC, the states of water in the NR–g–PHEMA membranes appeared as the free water and non–freezing bound water and both increased with %GE. Swelling behavior of NR–g–PHEMA membranes in water–acetone mixtures was investigated. The membrane swelling showed a non–ideal behavior where a maximum swelling degree was found at certain concentrations of water–acetone mixtures. The water sorption selectivity of the membranes was enhanced when increasing %GE for low water content in the water–acetone mixtures. However, as increasing water content, the water sorption selectivity was declined.