Melt block copolymerization of e-caprolactone and l-lactide

Autor: Jan Feijen, Peter van de Witte, Pieter J. Dijkstra, Peter J.A. in 't Veld, Jennie Hamhuis, Esther M. Velner
Přispěvatelé: Faculty of Science and Technology, Biomaterials Science and Technology
Jazyk: angličtina
Rok vydání: 1997
Předmět:
Zdroj: Journal of polymer science. Part A: Polymer chemistry, 35(2), 219-226. Wiley
ISSN: 0887-624X
Popis: AB block copolymers of e-caprolactone and (L)-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 e-caprolactone was polymerized first. Ethanol initiated the polymerization of e-caprolactone producing a polymer with e-caprolactone derived hydroxyl end groups which after addition of L-lactide in the second step of the polymerization initiated the ring-opening copolymerization of L-lactide. The number-average molecular weights of the poly(e-caprolactone) blocks varied from 1.5 to 5.2 × 103, while those of the poly(L-lactide) blocks ranged from 17.4 to 49.7 × 103. 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 e-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 e-caprolactone derived hydroxyl end groups generated during the copolymerization of e-caprolactone with pre-polymers of L-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.
Databáze: OpenAIRE
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