CATIONIC INITIATION OF VINYL ETHER POLYMERIZATION INDUCED BY (4-R1C6H4)(4-R2C6H4)R3CX IN CONJUNCTION WITH SILICA - PRODUCING HIGHLY HEAD GROUP FUNCTIONALIZED POLYMERS

Addition of vinyl ethers to arylmethyl halides and silica at 0 and -78 degrees C results in the formation of polymers. The average molecular weight, the molecular weight distribution (MWD), and the head group f unctionality are strongly dependent on the structure of the arylmethyl halide and on the olefin/arylmethyl halide ratio. The heterogeneous i nduced polymerization depends not only on the temperature but also on the kind of silica used, e.g. Aerosil (Degussa) and Kieselgel 60 (KG 6 0) (Merck). We found that initiation with carbocations of the type (4- (RC6H4)-C-1)(4-(RC6H4)-C-2)(RC+)-C-3 (R-1, R-2 = H, CH3, OCH3; R-3 = H , C6H5) with an electrophilicity in the range of -5 > pK(R+) > -9 bear ing a chloride counterion yields highly head group functionalized poly mers. General mechanisms for the initiation and propagation step of th e surface-mediated cationic vinyl ether polymerization considering the influence of the counterion and the initiating carbocation are discus sed.