Cyclopolymerization of bifunctional monomers

Abstract

Cyclopolymerization of some divinyl compounds and dialdehydes is discussed. First, the polymerization results with o-divinylbenzene are re-viewed together with the introductory discussion on some problems of cyclopolymerization of divinyl compounds in general. In all of the radical, cationic and anionic polymerizations of o-divinylbenzene, the intramolecular cyclization reaction possesses higher activation energies than the intermolecular propagation, where both reactions are competitive. Catalyst and solvent effects are demonstrated for the cyclization process in the ionic polymerization, loose propagating ion pairs apparently increasing the extent of cyclization. And propagation mechanisms are suggested which take into consideration the catalyst effect and the solvent effect. In the following sections, it is shown that some dialdehydes, which are expected to form five or six membered ring by cyclization, polymerize readily to give highly cyclized polymers. The cationic polymerization of o-phthalalde-hyde is shown to involve a “living” growing cation, and the steric structure of poly(o-phthalaldehyde) varies with the polymerization conditions. The capacity to cyclize, i.e. to form five or six-membered rings, is considered to be an important driving force for the polymerization of aromatic dialdehydes, e.g. o-phthalaldehyde and o-formylphenylacetaldehyde, in contrast to the nonpolymerizability of benzaldehyde. Generally speaking the structural characteristics, when the two functional groups are present at the vicinal position (ortho position) of the six-membered ring, provide great steric advantages for cyclopolymerization with all the monomers studied. However, propagation schemes are quite different among these monomers. Stepwise propagation is proposed for the cationic polymerization of o-divinylbenzene, and an intermediate or concerted scheme for those of dialdehydes and 1, 2-divinylcyclohexane. Moreover, it is concluded that both of these reaction schemes probably coexist in the cationic polymerization of o-divinylbenzaldehyde, depending on the kind of cation produced. © 1970, Walter de Gruyter. All rights reserved.