Using atom transfer radical polymerization for the synthesis of grafted PVDF copolymers towards the synthesis of membranes

Graft copolymers of poly(vinylidene fluoride) (PVDF) with poly(3-sulfopropyl methacrylic acid) (PVDF-g-PSPMA), poly(styrene-4-sulfonic acid) (PVDF-g-PSSA), and poly(dimethylaminoethyl methacrylate) (PDVFg-PDMAEMA) were synthesized. The aforementioned grafted copolymers were prepared from the corresponding (PDVF-g-PSPMPS) poly(3-sulfopropyl methacrylate potassium) and (PVDF-g-PSSS) poly(styrene-4-sulfonate sodium) salts using PVDF as a macroinitiator for atom transfer radical polymerization (ATRP). The copolymers were casted into membranes by the phase inversion method in aqueous media. The effects of polymerization time, degree of conversion, chain transfer agent (CTA) additive, crosslink process, and various solvents were investigated. The products were characterized by ¹H and ¹³C NMR spectroscopy, IR spectroscopy, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The maximum grafting incorporation was up to 26, 20 and 20 wt % for PSSA, PSPMA and PDMAEMA, respectively. The incorporation was reduced using a CTA additive. The most impressive feature of the graft copolymer membranes produced in this study are the improved water fluxes and polyethylene glycol (PEG) rejection properties when compared to the commercially available, pristine PVDF.