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 onto 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. silica. we adsorbed PVFA-co-PVAm samples of different molecular masses and co-polymer compositions from aqueous solutions onto 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 onto gold-coated silicon wafer surfaces was used to build up laterally patterned surfaces for sensors and biological applications.

Two different radical polymerization techniques have been applied to covalently graft vinyl formamide (VFA) onto silica particles. Grafting by the polymerization of VFA using an immobilized azo initiator on silica has been found less effective, because monomer conversion is limited in non-aqueous solvents and grafting yields are low in water. Radical copolymerization of VFA with vinyltriethoxysilane (VTS)-functionalized silica particles is suitable to produce poly(vinylformamide) (PVFA) silica hybrid particles in respectable yield. The VFA/VTS-co-grafted silica particles can be acidically hydrolyzed into poly(vinylamine)-grafted silica particles. Molecular structures of the surface groups and grafted polymer chains have been confirmed by means of solid state C-13{H-1} cross-polarization magic-angle spinning (CP MAS) NMR spectroscopy. Zeta potential measurements show the altering of the former silica particles surface charges arising from the introduction of basic groups on the surface.

Novel gold/poly-(1,3-divinyl-imidazolid-2-one)/silica [poly-bisvinylethyleneurea (poly-BVU)/silica)] hybrid particles have been produced by adsorption and spontaneously occurring in situ reduction of Au(3+) cations on the surface of poly-BVU/silica hybrid particles. The successful functionalization of the poly-BVU/silica particles with gold nanoclusters has been evidenced by UV/vis and XPS spectroscopy as well as scanning electron microscopy. The size of the resulting gold clusters, estimated by means of the Mie-Drude theory on the full peak width at half-maximum of the surface plasmon UV/vis absorbance, correlates with the polymer content of the poly-BVU/silica hybrid particles used for the modification. Therefore, it is possible to control the size of the gold clusters simply by adjusting the monomer/silica ratio in the polymerization process, which corresponds with the polymer content of the hybrids.

Polyvinylamine hydrogels with silica particles encapsulated (PVAm/silica) were produced by a two-step synthesis. In the first step, polyvinylformamide/silica (PVFA/silica) hybrids were synthesized from vinylformamide (VFA) and 1,3-divinylimidazolidin-2-one (1,3-bisvinylethyleneurea, BVU), as the crosslinker, by radical copolymerization in silica/water suspensions using different compositions of VFA/BVU. The target product PVAm/silica was obtained by acidic hydrolysis of the PVFA/silica hydrogels in a second step. The chemical structures of both hydrogels, PVFA/silica and PVAm/silica, respectively, were revealed by solid-state C-13(H-1) cross-polarity/magic-angle spinning NMR spectroscopy. Both hydrogels swelled significantly in water. The swelling capacity of the two systems was characterized by the correlation length (or hydrodynamic blob size) of the network meshes with small-angle neutron scattering experiments. is significantly larger for PVAm/silica than for PVFA/silica, which corresponds to the observed higher swelling capacity of this polyelectrolyte material. Furthermore, the swelling behavior of the hybrid hydrogels was quantitatively described in terms of free swell capacity, centrifuge-retention capacity, adsorption against pressure, and free swell rate as compared with values of the corresponding copolymer hydrogels. (C) 2002 Wiley Periodicals, Inc.

The use of vinylformamide and 1,3-divinylimidazolidin-2-one, bisvinylethylene-urea (BW), as well as of the poly(vinylformamide-vinylamine) copolymer (PVFA-co-PVAm) for silica surface functionalization has been investigated. Various procedures such as grafting from, crosslinking surface polymerization, and post-functionalization of adsorbed PVAm chains have been experimentally applied. The advantage of the different synthetic methods is discussed with regard to the resulting surface structure of the organic/inorganic hybrid materials.

For quantitative metal salt adsorption, poly(1,3-divinylimidazolid-2-one)/silica [poly BVU(cat.)/silica] particles with different polymer contents have been synthesized by a cationic surface polymerization of 1,3-divinylimidazolid-2-one onto silica. Preliminary experiments with the metal ion salts CoCl(2), CoI(2), CuCl(2), and FeCl(3) on poly-BVU(cat.)/silica particles, a radically produced poly-BVU(rad.) resin, and a cationically produced poly-BVU(cat.) resin have been carried in acetone solution to check the suitability of the adsorbents. The adsorption mechanism for Co(2+) and Cu(2+) on poly-BVU(cat.)/silica is in accordance with the Langmuir model for monolayer adsorption as shown by quantitative adsorption measurements by means of UV/vis spectroscopy. An ion pair adsorption mechanism is suggested for CoCl(2), CoI(2), and CuCl(2) on poly-BVU(cat.)/silica because both environments cationically produced poly-BVU and residual silanol groups are required for linking the cation and anion. ESR spectroscopic results of CoCl(2)-, CuCl(2)-, and FeCl(3)-poly-BVU(cat.)/silica hybrid adsorbates show selective adsorption for Co(2+) and Cu(2+). However, two different adsorption sites are indicated for Fe(3+) on poly-BVU(cat.)/silica. Copyright 2001 Academic Press.

The cationic polymerization of the bifunctional monomer 1,3-divinylimidazolid-2-one (BVH) is initiated by triphenylmethylium/silica hybrid particles in toluene or 1,2-dichloroethane (DCE) as solvents. Novel poly-BVH/silica hybrid particles are obtained by this procedure. The degree of surface functionalization can be controlled by the BVH concentration and the solvent used. The cationic polymerization of BVH on the surface of silica particles is strongly determined by proton transfer reactions to the monomer. Therefore, the BVH polymer network on the silica particle contains methyl groups and double bonds among the urea units.