Novel synthesis of biodegradable star poly(ethylene glycol)‐block‐poly(lactide) copolymers |
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Authors: | Yahia Lemmouchi Michael C. Perry Allan J. Amass Khirud Chakraborty Etienne Schacht |
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Affiliation: | 1. Chemical Engineering and Applied Chemistry, Aston University, Aston Triangle, Birmingham B4 7ET, United Kingdom;2. Chemical Engineering and Applied Chemistry, Aston University, Aston Triangle, Birmingham B4 7ET, United KingdomChemical Engineering and Applied Chemistry, Aston University, Aston Triangle, Birmingham B4 7ET, United Kingdom;3. Robinson Brothers Limited, Phoenix Street, West Bromwich B70 0AH, United Kingdom;4. Polymer Chemistry and Biomaterials Research Group, Ghent University, Krijgslaan 281 S‐4, B‐9000 Ghent, Belgium |
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Abstract: | Biodegradable star‐shaped poly(ethylene glycol)‐block‐poly(lactide) copolymers were synthesized by ring‐opening polymerization of lactide, using star poly(ethylene glycol) as an initiator and potassium hexamethyldisilazide as a catalyst. Polymerizations were carried out in toluene at room temperature. Two series of three‐ and four‐armed PEG‐PLA copolymers were synthesized and characterized by gel permeation chromatography (GPC) as well as 1H and 13C NMR spectroscopy. The polymerization under the used conditions is very fast, yielding copolymers of controlled molecular weight and tailored molecular architecture. The chemical structure of the copolymers investigated by 1H and 13C NMR indicates the formation of block copolymers. The monomodal profile of molecular weight distribution by GPC provided further evidence of controlled and defined star‐shaped copolymers as well as the absence of cyclic oligomeric species. The effects of copolymer composition and lactide stereochemistry on the physical properties were investigated by GPC and differential scanning calorimetry. For the same PLA chain length, the materials obtained in the case of linear copolymers are more viscous, whereas in the case of star copolymer, solid materials are obtained with reduction in their Tg and Tm temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3966–3974, 2007 |
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Keywords: | biodegradable polyesters poly(ethylene glycol) poly(lactide) ring‐opening polymerization star copolymers |
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