Silver perchlorate‐initiated polymerization of vinyl monomers

Abstract

AbstractThe polymerization of vinyl compounds can be initiated by soluble silver salts. In this paper, the kinetics of the silver perchlorate‐initiated polymerization of styrene and methyl methacrylate in organic solution has been examined. The rates were measured dilatometrically at 70°C.; the solutions were prepared by a high vacuum technique. With respect to the monomer, either styrene or methyl methacrylate, the order of reaction is equal to two. In the case of styrene, the rate of polymerization is proportional to the silver perchlorate concentration when this concentration is ≤ 102 mole/l. Above this value, the rate becomes proportional to the square of the silver perchlorate concentration. For methyl methacrylate, the order with respect to the silver salt concentration varies from 0.5 to 1, depending on the concentration range. These kinetic results are interpreted on the basis of the assumption that a silver perchlorate–monomer complex, instead of a silver perchlorate molecule, participates in the polymerization. Moreover, the examination of styrene and benzene solutions of silver perchlorate indicates a formation of silver salt–aromatic hydrocarbon complexes of the 1:1 and 2:1 types. Consequently, good agreement is found between the kinetics of those two different initiator systems. A coordination polymerization mechanism is proposed, in which hydrogen transfer alternates with each propagation step. The mechanism is corroborated by an isotope effect equal to two, when dideuterostyrene is compared to styrene. The internal structure of the poly(methylmethacrylate) obtained with AgClO4, corresponds to that of a conventional polymer. The presence of traces of water inhibits the polymerization.