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More about the polymerization of lactides in the presence of stannous octoate

✍ Scribed by G. Schwach; J. Coudane; R. Engel; M. Vert

Publisher: John Wiley and Sons
Year: 1997
Tongue: English
Weight: 212 KB
Volume: 35
Category: Article
ISSN: 0887-624X
DOI: 10.1002/(sici)1099-0518(19971130)35:16<3431::aid-pola10>3.0.co;2-g

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✦ Synopsis

The ring-opening polymerization of lactide cyclic monomers in the bulk in the presence of tin(II) 2-ethylhexanoate (stannous octoate or SnOct 2 ) was reexamined under conditions allowing for the end group characterization of growing chains by highresolution 1 H-NMR. Data collected for low values of the monomer/initiator (M/I) ratio showed that the DL-lactide ring was opened to yield lactyl octoate-terminated short chains. A cationic-type mechanism involving co-initiation by octanoic acid was proposed to account for experimental findings. The formation of a side product, hydroxytin(II) lactate (HTL), was found which appeared able to initiate lactide polymerization and to yield a high molecular weight PLA50 polymer. However the polymerization with stannous octoate was faster than the HTL one. Anyhow, data suggested that both SnOct 2 and HTL are likely to act simultaneously as initiators during the polymerization of lactides in the presence of SnOct 2 . A complete reaction scheme was proposed to account for the presence of the various compounds likely to be formed under these conditions.

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