Tailoring of Teflon-Fep Film through Graft-Copolymerization with Polar Monomers for Desalination Processes: Effect of Swift Heavy Ion Irradiation

Abstract

In the present communication we report on the grafting of 4-vinyl pyridine (4-VP) and methacrylic acid (MAAc) onto Teflon-FEP film by a preirradiation method to synthesize ionic membranes. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage of grafting of 4-VP (13.66%) was obtained at an optimum total dose of 58.3 kGy at [4-VP] = 1.9 moles/L while MAAc produced 66.40% of maximum grafting at optimum conditions of 39.74 kGy total dose using [MAAc] = 2.5 moles/L in 10 ml of water. Effect of dose rate on grafting of 4-VP has also been discussed. The optimum conditions were used to graft 4-VP and MAAc onto Teflon-FEP film irradiated at different fluence with Swift heavy ions (SHIs). Better grafting of 4-VP was obtained in the SHI irradiated films while MAAc produced lower grafting. The membranes were characterized by FTIR spectroscopy, scanning electron microscopy and thermo gravimetric analysis. Swelling studies of the membranes were performed in different polar solvents such as water, ethanol (EtOH), dimethyl sulphoxide (DMSO) and dimethyl formamide (DMF). Teflon-FEP-g-poly(4-VP) showed maximum swelling in water whereas in case of Teflon-FEP-g-poly (MAAc), maximum swelling was observed in DMSO. Conductance measurements in aqueous sodium chloride solution showed that these membranes have an affinity for Na+ ions and Cl- ions and hence can be used in desalination processes for the separation of ions.