CONTROLLED POLYMERIZATION OF CYCLIC ESTERS - STRUCTURE OF INITIATORS AND OF ACTIVE SPECIES-RELATED TO THE SELECTIVITY OF INITIATION AND PROPAGATION

This paper reviews mostly the already published work of our own, compl emented with some new data and related to the control (i.e. selectivit y) in the anionic and covalent (pseudoanionic) polymerization of cycli c esters. Ionic and covalent growing species are briefly compared in t erms of their susceptibility to undergo side reactions. Then, structur es of covalent initiators (mostly multivalent metal alkoxides) are dis cussed from the view point of their behavior in initiation and formati on of active species. R2AlOR', (RO)(3)Al, and other metal alkoxides ar e discussed.