Synthesis and structural study of copolymers of l-lactic acid and bis(2-hydroxyethyl terephthalate) |
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Authors: | Ewa Olewnik Wojciech Czerwiński Marie-Odile Sepulchre Martine Tessier Slim Salhi Alain Fradet |
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Affiliation: | a Nicolaus Copernicus University, Faculty of Chemistry, Department of Physical Chemistry, 7 Gagarin Street, 87100 Toruń, Poland b Université Pierre et Marie Curie-Paris 6, Laboratoire de Chimie des Polymères, Courrier 184, 4 Place Jussieu, 75252 Paris Cedex 05, France c CNRS, UMR 7610, Paris, France |
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Abstract: | Poly(ethylene terephthalate)-poly(lactic acid) (PET-PLLA) copolyesters were synthesized by the melt reaction of bis(2-hydroxyethyl terephthalate) (BHET) with l-lactic acid oligomers (OLLA) in the presence of SnCl2, H2O-p-toluene sulfonic acid, H2O catalytic system. The 1H and 13C NMR studies confirm the incorporation of lactate units in PET chains after reaction. Copolyesters containing nearly equimolar terephthalate/lactate ratio are not completely random and present some block-copolymer character, while the microstructure of PET-rich copolyesters is a random one. Due to a longer PET sequence length, the latter exhibit a melting point close to 210 °C while the other ones are amorphous. SEC/MALDI-TOF MS off-line coupling was used to obtain the absolute average molar masses of the copolyesters. The results indicate that the conventional polystyrene calibration method leads to a strong overestimation of PET-PLLA molar masses, while the determined by NMR is much closer to the SEC/MALDI value. |
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Keywords: | Biodegradable polymers Copolymerization l-Lactic acid" target="_blank">l-Lactic acid Polycondensation Poly(ethylene terephthalate) |
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