APPLICATION OF CATIONIC POLYMERIZATION TO GRAFTING AND COATING OF SILICA PARTICLES

The cationic polymerization of electron rich monomers such as vinyl et hers, vinyl furane, and cyclopentadiene on silica surfaces can be init iated by aryl methyl halides. The reactions yield always soluble polym ers (by heterogeneous catalysis) and novel polymer/silica hybrid mater ials. The link between polymer and solid is caused by covalent Si-O-C bonds, by network formation of the polymers during the chain growth, o r by a combination of both of them. The analysis of the polymer struct ures on the surface by H-1 MAS NMR spectroscopy in suspension and by s olid state C-13 CP MAS NMR spectroscopy is described. Proof of Si-O-C bonds via DRIFT spectroscopy and C-13 CP MAS NMR spectroscopy is given . The most effective method of irreversibly linking the polymer to the silica surface is the network formation. Polyvinyl ethers are bound s trongly to the surface, as can be shown by FTIR measurements, but the linkage is not stable due to the Si-O-C bonds' susceptibility to hydro lysis. Poly-cyclopentadienes (PCPD) are linked to the surface by Si-O- C bonds, which show an extraordinary high resistance to acids and base s. Si-O-C bond formation of poly-2-vinyl furane could not yet be detec ted by C-13 CP MAS NMR spectroscopy and DF:IFT spectroscopy. In this c ase the high degree of coating derives from the bifunctionality of 2-v inyl furane: it may undergo Friedel-Crafts-alkylation at the 5-positio n of the furane ring as well as chain polymerization via the vinyl gro up at the 2-position.