STRUCTURE OF POLYETHYLENE-GRAFT-POLYSTYRENE SULFONIC ACID MEMBRANES PREPARED BY RADIATION-INDUCED GRAFTING

Structural behavior of polyethylene- graft-polystyrene sulfonic acid (PE- g-PSSA) membranes prepared by simultaneous radiation-induced grafting of styrene onto low density polyethylene (PE) films followed by sulfonation was investigated. FTIR, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to monitor the changes in the morphology and the crystallinity taking place in the membranes during the applied two step preparation procedure (grafting and sulfonation) and the variation of the degree of grafting. Thermal properties such as melting temperature (Tm) and the heat of melting (ΔHm) were also studied. The membranes showed a chemical structure of strongly hydrophilic nature due to the presence of (SO3 −) groups with their associated water molecules. Both grafting and subsequent sulfonation were found to induce significant structural changes in the PE matrix. The overall crystallinity of the membranes was found to decrease with the increase in the degree of grafting and that is attributed to the cumulative effect of dilution and partial disruption of the inherent crystallites of the PE films.