Hydrolytic degradation of polyisobutylene and poly‐L‐lactide–based multiblock copolymers |
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Authors: | Umaprasana Ojha Pallavi Kulkarni David Cozzens Rudolf Faust |
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Affiliation: | Department of Chemistry, University of Massachusetts Lowell, One University Avenue, Lowell, Massachusetts 01854 |
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Abstract: | The hydrolytic degradation of a series of poly‐L ‐lactide (PLLA)‐polyisobutylene (PIB) multiblock copolymers was studied in phosphate buffer solution (pH = 7.4) at 37 °C. The multiblock copolymers were synthesized by chain extension of PLLA‐b‐PIB‐b‐PLLA triblock copolymers, which were obtained by ring‐opening polymerization of L ‐lactide initiated by hydroxyallyl telechelic PIB. The degradation strongly depended on the PLLA segment length. At constant PIB segment length, the multiblock copolymer with the shortest PLLA segment length (DPn = 10), showed significant weight loss after 8 weeks, whereas weight loss for DPn = 36 was only observed after 24 weeks. The gel‐permeation chromatographic analysis showed a similar decrease in the number‐average molecular weight (Mn) with time further supporting the weight loss data. Dynamic mechanical analysis showed a decrease in ultimate stress and modulus with time. The crystallinity of multiblock copolymers changed significantly with degradation time as indicated from differential scanning calorimetric analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3767–3774, 2010 |
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Keywords: | block copolymers biomaterials hydrolytic stability polyurethanes |
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