MACROMOLECULAR ENGINEERING OF POLYLACTONES AND POLYLACTIDES .12. STUDY OF THE DEPOLYMERIZATION REACTIONS OF POLY(EPSILON-CAPROLACTONE) WITH FUNCTIONAL ALUMINUM ALKOXIDE END-GROUPS

Ring-opening polymerization of epsilon-caprolactone has been initiated with functional aluminum alkoxides in toluene at 25-degrees-C. Degradation of ''living'' polyester chains by transesterification reactions has been studied in relation to temperature, solvent polarity, average molecular weight, and structure of the initiator, i.e., the nature of the functional group and the number of alkoxides per Al atom. Degradation products, particularly cyclic oligomers, have been isolated by supercritical fluid extraction (SFE) and characterized by GC-MS. The effect of Lewis bases on transesterification reactions has been investigated and discussed in reference to the ''coordination-insertion'' mechanism.