Macromolecular engineering of polylactones and polylactides

Summary Aluminum alkoxides carrying functional alkoxy groups are effective initiators for the-caprolactone polymerization in toluene and tetrahydrofuran. The coordination-insertion type of polymerization is living and yields exclusively linear polyesters of a predictable molecular weight with a narrow molecular weight distribution within the period of time required for the total monomer conversion. The functional group associated to the active alkoxy group of the initiator is selectively attached to one chain-end, and the second end-group is systematically a hydroxyl function resulting from the hydrolysis of the living growing site. Asymmetric telechelic polyesters are thus obtained in a perfectly controlled way, including macromonomers. Beside (meth)acrylic double bond, the functional end-group derived from the initiator can be, for instance, an unsaturation, a halogen and a tert-amine. Coupling the asymmetric telechelic polymer via the OH end-group (or the precursor Al alkoxide end-group) is a direct way to the related symmetric telechelic of a twofold increased molecular weight.The authors are indebted to IRSIA for a fellowship to one of them (Ph. Dubois) and to the Services de la Programmation de la Politique Scientifique for financial support. NMR spectra were recorded at the CREMAN facility of the University of Liège which has been funded by a grant from the Fonds National de la Recherche Scientifique. The helpful assistance of Dr. Warin has been very much appreciated. They are very greatful to G. Broze (Colgate Palmolive) who initiated this research.