Macromolecular Engineering of Polylactones and Polylactides. 11. Synthesis and Use of Alkylaluminum Dialkoxides and Dithiolates as Promoters of Hydroxy Telechelic Poly(ϵ-caprolactone) and α,ω)-Dihydroxy Triblock Copolymers Containing Outer Polyester Blocks

Diethylaluminum dialkoxides (Et₂A10XOAlEt₂, 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 ϵ-caprolactone. Hydroxy telechelic poly(ϵ-caprolactone) and α,ω-dihydroxypoly(ϵ-caprolactone-b-X-b-ϵ-caprolactone) have been accordingly prepared and characterized. A hydroxy group is selectively attached at both ends as demonstrated by IR and ¹H NMR spectroscopies and confirmed by titration of the derivatized α,ω-dicarboxylic acid (co)polymers. Polymerization of ϵ-caprolactone is living and yields linear polyester chains of a predictable molecular weight and of quite a narrow molecular weight distribution.