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Melt block copolymerization of ϵ-caprolactone and L-lactide

✍ Scribed by Peter J. A. In't Veld; Esther M. Velner; Peter Van De Witte; Jennie Hamhuis; Pieter J. Dijkstra; Jan Feijen

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
767 KB
Volume
35
Category
Article
ISSN
0887-624X

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✦ Synopsis

AB block copolymers of c-caprolactone and ([.) -lactide could be prepared by ring-opening polymerization in the melt at 110"C using stannous octoate as a catalyst and ethanol as an initiator provided c-caproiactone was polymerized first. Ethanol initiated the polymerization of c-caprolactone producing a polymer with c-caprolactone derived hydroxyl end groups which after addition of 1,-lactide in the second step of the polymerization initiated the ring-opening copolymerization of L-lactide. The number-average molecular weights of the poly(c-caprolactone) blocks varied from 1.5 to 5.2 X 10a, while those of the poly(l.lactide) blocks ranged from 17.4 to 49.7 X 10s. The polydispersities of the block copolymers varied from 1.16 to 1.27. The number-average molecular weights of the polymers were controlled by the monomer/hydroxyl group ratio, and were independent on the monomer/ stannous octoate ratio within the range of experimental conditions studied. When L-lactide was polymerized first, followed by copolymerization of c-caprolactone, random copolymers were obtained. The formation of random copolymers was attributed to the occurrence of transesterification reactions. These side reactions were caused by the c-caprolactone derived hydroxyl end groups generated during the copolymerization of c-caprolactone with prepolymers of 1,-lactide. The polymerization proceeds through an ester alcoholysis reaction mechanism, in which the stannous octoate activated ester groups of the monomers react with hydroxyl groups. .C 1997.JohnWiley & Sons, Inc.

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