Poly(Vinylformamide- co -Vinylamine)/Inorganic Oxide Hybrid Materials

Abstract

Novel ways to synthesize poly(vinylamine)/silica hybrid materials rich in free amino moieties using vinylformamide (VFA) as the key monomer are reported. Such materials are accessible from poly(vinylamine) which is obtained from radically produced poly(vinylformamide) (PVFA) which was either immobilized on to silica surfaces from solution and converted into poly(vinylamine- co -vinylformamide) polymers (PVFA- co -PVAm) by acidic hydrolysis, or by acidic hydrolysis in solution with subsequent adsorption on to silica. We adsorbed control PVFA- co -PVAm samples of different molecular masses and co-polymer compositions from aqueous solutions on to inorganic surfaces such as silica or titania simply by pH control. Direct surface functionalization using the VFA monomers was possible by their radical graft co-polymerization with bifunctional monomers, for example 1,3-divinylimidazolid-2-one (BVU) or on silica particles which were pre-functionalized with vinyltriethoxysilane (VTS). The influence of the amino content and molar mass (4000, 40,000, and 400,000 g mol−1) of PVFA- co -PVAm on the degree of surface coverage, charging, and polarity was studied using X-ray photoelectron spectroscopy (XPS), potentiometric titrations, and electrokinetic measurements, and solvatochromic probes. It was shown that the amino content of the co-polymer has a significant influence on the amount of polymer adsorbed, the layer thickness, and surface polarity. Post-functionalization reactions with isocyanates or fullerene were used as a suitable method for enhancing the stability of the polyelectrolyte layer on the inorganic surface. They also open the way to producing multi-functional hybrid materials. The adsorption and post-functionalization of PVFA- co -PVAm samples on to gold-coated silicon wafer surfaces was used to build up laterally patterned surfaces for sensors and biological applications.