Synthesis and characterization of poly(L‐lactide‐co‐ϵ‐caprolactone)‐b‐poly(L‐lactide) biodegradable diblock copolyesters: Effect of the block lengths on their thermal properties |
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Authors: | Noi Niamsa Yodthong Baimark |
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Affiliation: | Department of Chemistry, Faculty of Science, Mahasarakham University, Mahasarakham 44150, Thailand |
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Abstract: | Poly(L ‐lactide‐co‐ε‐caprolactone)‐b‐poly(L ‐lactide) P(LL‐co‐CL)‐b‐PLL] diblock copolyesters were synthesized in a two‐step process with 1‐dodecanol (DDC) and stannous octoate as the initiating system. In the first‐step reaction, a 50:50 mol % amorphous poly(L ‐lactide‐co‐ε‐caprolactone) P(LL‐co‐CL)] copolyester was synthesized via the bulk copolymerization of L ‐lactide and ε‐caprolactone, which was followed by the polymerization of the PLL crystalline block at the end chain in the second‐step reaction. The yielded copolyesters were characterized with dilute‐solution viscometry, gel permeation chromatography, 1H‐ and 13C‐NMR, and differential scanning calorimetry methods. The molecular weights of the P(LL‐co‐CL) copolyesters from the first‐step reaction were controlled by the DDC concentrations, whereas in the second‐step reaction, the molecular weights of the P(LL‐co‐CL)‐b‐PLL diblock copolyesters depended on the starting P(LL‐co‐CL) copolyester molecular weights and L ‐lactide/prepolymer molar ratios. The starting P(LL‐co‐CL) copolyester molecular weights and PLL block lengths seemed to be the main factors affecting specific thermal properties, including the melting temperature (Tm), heat of melting (ΔHm), crystallizing temperature (Tc), and heat of crystallizing (ΔHc), of the final P(LL‐co‐CL)‐b‐PLL diblock copolyester products. Tm, ΔHm, Tc, and ΔHc increased when the PLL block lengths increased. However, these thermal properties of the diblock copolyesters also decreased when the P(LL‐co‐CL) block lengths increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 |
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Keywords: | biodegradable biomaterials block copolymers diblock copolymers thermal properties |
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