Cationic ring-opening polymerization.

Abstract

Advances in the major areas of the ca-tionic ring-opening polymerizations are discussed. In the first part synthesis of new polymers is reviewed ; this includes mainly novel block and graft copolymers based on the di-and multicationically ended living polyacetals and polyethers (polyTHF). Recent data on thermodynamics of nonideal systems , giving dependence of [M]e on [M],,are summarized with special emphasize of the differences between monomers due to variation of their nucle-ophilicities. rization of cyclic acetals and ethers is focused on the macroring formation and reactivities of active centers. The reactivity of covalent and various ionic growing species are compared in the polymeriza-tion of cyclic ethers (THF and oxepane) and oxazo-lines. Reasons for much lower reactivity of cova-lent than ionic species and reasons for similar reactivities of macroion-pairs and macroions are presented. It is shown, that the kinetically controlled proportions of macrorings in the polymerization of these and other heterocyylic mnomers depend on the structure of the end-groups, forred upon initiation. Initiation with acids, giving H-X-(where X=heteroatom) end-groups, ie~.:s to the kinetically enhanced proportion of macrorings. This is particularly important for the low degrees of polymerization.