Résumé
The direct surface modification of poly(vinylidene fluoride-co-trifluoroethylene) (VDF-co-TrFE) copolymerfilms via surface-initiated atom transfer radical polymerization (ATRP) is presented. The surface-initiatedATRP of tert-butyl acrylate (tBA) and styrene was carried out on poly(VDF-co-TrFE) films containing 75mol% VDF at 383 K. Such a reaction was monitored by 1H and 19F NMR, attenuated total reflectanceFourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and by watercontact angle measurements. First, the 19F NMR spectra of poly(VDF-co-TrFE)-g-poly(tBA) graftcopolymers revealed a reduction in the signal intensity at 123 ppm compared with that of the poly(VDFco-TrFE) copolymer, indicating that the polymerization of tBA occurred exclusively by fluorine abstractionfrom the TrFE units. ATR-FTIR spectra of the resulting poly(VDF-co-TrFE)-g-poly(tBA) and poly(VDF-co-TrFE)-g-polystyrene (PS) films evidenced the characteristic absorption frequencies assigned to carbonyl andaromatic C–H stretching. The atomic ratio on the surface of polymer-grafted poly(VDF-co-TrFE) filmobserved by XPS well agreed with theoretical value of poly(tBA) and PS hompolymers. These resultsindicated that poly(tBA) and PS were successfully grafted onto the poly(VDF-co-TrFE) film surfaces forminggrafting layers, the thickness of which was over 10 nm. The poly(VDF-co-TrFE)-g-poly(tBA) film wassubsequently treated with p-toluenesulfonic acid and sodium hydrogen carbonate to modify the graftedchains into poly(acrylic acid sodium salt). Surface-grafted polystyrene was also converted to poly(styrenesulfonic acid sodium salt) by treatment with sulfonic acid. Each reaction step was characterized by ATR-IRand XPS. The static water contact angle of poly(VDF-co-TrFE) copolymer was remarkably reduced from 91to 15 by hydrolysis of the tBA chains, sulfonation of the styrene chains and their neutralization. Ahydrophilic surface was successfully achieved on the poly(VDF-co-TrFE) film by direct surface-initiatedpolymerization fromthe outermost surface of the TrFE unitwithout any change in the bulk physical properties.