CATIONIC POLYMER SYNTHESIS AT INORGANIC S URFACES

Cationic vinyl polymerizations at inorganic acceptor surfaces (alumina and silica) advantageously occur via ion pair intermediates as shown in the following scheme 1: [GRAPHICS] The main principle holds that sp ecies that are dormant in the surrounding liquid phase become cationic ally active when they interact with surface groups. Thus, carbenium io n pair chemistry is possible only when active species are present in t he interfacial frontier because carbenium-anion recombination takes pl ace as a diffusion-controlled process in solution. The balance of the equilibrium is evidently controlled by both the Lewis acidity of the c arbenium ion arid the basicity of the corresponding counterion. Anew c ationic interfacial initiator was obtained by the simple adsorption pr ocess of S(N)1-active arylmethylhalides onto acidic silica surface und er inert conditions. The mechanism of interfacial initiation has been investigated by means of classical adsorption techniques, UV spectrosc opy, and electrokinetic measurements. The properties of dormant polyme rs and, ''living''-polymers-modified surfaces are discussed with respe ct to the mechanism of cationic polymerization and colloid chemistry.