Polylactones 27. Anionic polymerization of L-lactide. Variation of endgroups and synthesis of block copolymers with poly(ethylene oxide)
| Autor: | Caroline Boettcher, Hans R. Kricheldorf |
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| Rok vydání: | 1993 |
| Předmět: |
Materials science
Polymers and Plastics Ethylene oxide Organic Chemistry Diethylene glycol Ether Condensed Matter Physics chemistry.chemical_compound Anionic addition polymerization chemistry Polymerization Polymer chemistry Materials Chemistry Copolymer Organic chemistry Ethylene glycol Racemization |
| Zdroj: | Makromolekulare Chemie. Macromolecular Symposia. 73:47-64 |
| ISSN: | 0258-0322 |
| DOI: | 10.1002/masy.19930730107 |
| Popis: | L-Lactide was polymerized in toluene with various alkoxide initiators. These initiators were prepared in situ from potassium t.-butoxide and primary or secondary alcohols such as tetradecanol, diethylene glycol butyl ether, menthol or testosteron. All these alcohols were incorporated as ester endgroups into the polylactide chain. However 1H-NMR spectroscopy proves the existence of more OH-endgroup than ester endgroups. This finding and 10–20% racemization observed for all anionic polymerizations suggest that chain-transfer reactions with the monomer via deprotonation take place. When poly(ethylene glycol) monomethyl ether in combination with KOtBu was used as initiator, twoblock copolymers were obtained. With poly(ethylene glycol) A-B-A-triblock copolymers could be synthesized. The quantitative reaction of the poly(ethylene glycol)s with L-lactide could be proven by both 1H NMR spectroscopy and gelpermeation chromatography. DSC-measurements show that depending on their lengths either the polylactide or the poly(ethylene oxide)blocks can crystallize. Due to partial racemization the melting temperatures (Tm) of the poly(L-lactide) blocks did not exceed 155°C. |
| Databáze: | OpenAIRE |
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