On the preparation and application of novel PVDF–POSS systems

Novel systems based on poly(vinylidene fluoride) (PVDF) and polyhedral oligomeric silsesquioxane (POSS) have been prepared by grafting amino-containing POSS (POSS–NH2) onto the surface of modified PVDF (PVDFm). Namely, the approach consists of a preliminary modification of PVDF by a chemical treatment with an alkaline solution, in order to obtain unsaturations, and a subsequent surface reaction of PVDFm with POSS molecules characterized by an amino group as reactive side. The level of polymer unsaturation, measured by Raman spectroscopy, turned out to be finely tuned by varying the dehydrofluorination reaction time. The surface grafting of POSS has been studied by SEM-EDS analysis, Raman and XPS spectroscopy. Indeed, while the level of modification of PVDFm has been found to decrease as a consequence of the reaction with POSS, thus indicating a likely saturation of double bonds by silsequioxane molecules, the Si concentration turned out to increase with increasing the concentration of the polymer surface unsaturation. The feasibility of the application of POSS grafting onto the surface of membranes, based on PVDFm, has also been verified.