Cationic Interracial Polymerization ofp-Methoxystyrene by Means of Triphenylmethylium Halide-Aerosil Initiation

Abstract

Cationic polymerizations of p-methoxystyrene initiated by triphenylmethylium halides in conjunction with silica surfaces proceed via ion pair intermediates. The polymerization yields both aerosil-polymer composites and soluble polymers. The triphenylmethylium halides are active only on the surface of the solid, which is demonstrated by means of adsorption and zeta-potential measurements in 1,2-dichloroethane. The influence of the overall monomer concentration and initiator concentration on the MWD curves and composite formation is discussed in relation to the mechanism of cationic polymerization. Triphenylmethylium bromide-aerosil adsorbates yield soluble polymers with narrow MWD curves (M _w/M _n ≃ 1,2). This behavior approaches living conditions. The formation of composites mainly proceeds in the Stern layer of the ion pair layer which covers the aerosil particle while the generation of soluble polymers occurs in the diffuse layer. The behavior of interfacial polymerization is discussed in relation to surface chemistry and the mechanism of cationic polymerization. A general model for interfacial polymerization is proposed for triphenylmethylium halide-aerosil initiation.