MACROMOLECULAR ENGINEERING OF POLYLACTONES AND POLYLACTIDES .11. SYNTHESIS AND USE OF ALKYLALUMINUM DIALKOXIDES AND DITHIOLATES AS PROMOTERS OF HYDROXY TELECHELIC POLY(EPSILON-CAPROLACTONE) AND ALPHA,OMEGA-DIHYDROXY TRIBLOCK COPOLYMERS CONTAINING OUTER POLYESTER BLOCKS

Diethylaluminum dialkoxides (Et2AlOXOAlEt2, where X is either an aliphatic radical or a polymer chain) and related dithiolates have been investigated as potential initiators for the ring-opening polymerization of epsilon-caprolactone. Hydroxy telechelic poly(epsilon-caprolactone) and alpha,omega-dihydroxypoly(epsilon-caprolactone-b-X-b-epsilon-caprolactone) have been accordingly prepared and characterized. A hydroxy group is selectively attached at both ends as demonstrated by IR and H-1 NMR spectroscopies and confirmed by titration of the derivatized alpha,omega-dicarboxylic acid (co)polymers. Polymerization of epsilon-caprolactone is living and yields linear polyester chains of a predictable molecular weight and of quite a narrow molecular weight distribution.