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- Title
Fast and Living Ring-Opening Polymerization of l-Lactide Initiated with In-situ–Generated Calcium Alkoxides.
- Authors
Zhong, Zhiyuan; Schneiderbauer, Stefan; Dijkstra, Pieter J.; Westerhausen, Matthias; Feijen, Jan
- Abstract
The ring-opening polymerization of l-lactide with calcium alkoxides generated in-situ from bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] and 2-propanol are presented. The polymerization in THF at room temperature proceeds rapidly and in a living manner, giving poly(l-lactide)s of controlled molecular weight, low polydispersity, and tailored end-functionalities. Kinetic studies show the absence of an induction period and a pseudo-first order rate constant of 6.41 L mol-1 min-1, which is significantly higher than for related Y5(μ-O)(OiPr)13- or aluminum alkoxide-initiated polymerizations. The initiation involves a two-step process: (1) alcoholysis of bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] to give the corresponding calcium alkoxide and (2) ring-opening of l-lactide via acyl-oxygen cleavage and insertion into the calcium-alkoxide bond. In the presence of excess alcohol, fast and reversible exchange between free alcohol molecules and coordinated alkoxide ligands takes place. This allows tuning of the poly(l-lactide) molecular weight over a wide range.
- Subjects
POLYMERIZATION; CHEMICAL reactions; ALKOXIDES; ORGANOMETALLIC compounds; CALCIUM; INDUCTION heating
- Publication
Journal of Polymers & the Environment, 2001, Vol 9, Issue 1, p31
- ISSN
1566-2543
- Publication type
Article
- DOI
10.1023/A:1016092420618