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 functionality are strongly dependent on the structure of the arylmethyl halide and on the olefin/arylmethyl halide ratio. The heterogeneous induced polymerization depends not only on the temperature but also on the kind of silica used, e.g. Aerosil (Degussa) and Kieselgel 60 (KG 60) (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 bearing a chloride counterion yields highly head group functionalized polymers. General mechanisms for the initiation and propagation step of the surface-mediated cationic vinyl ether polymerization considering the influence of the counterion and the initiating carbocation are discussed.