Polymerization of l-lactide with SnCl2: A Low Toxic and Eco-friendly Catalyst |
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Authors: | Kricheldorf Hans R. Weidner Steffen M. |
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Affiliation: | 1.Institut für Technische und Makromolekulare Chemie der Universit?t Hamburg, Bundesstr. 45, 20146, Hamburg, Germany ;2.BAM-Bundesanstalt für Materialforschung und -prüfung, Richard Willst?tter Str. 11, 12489, Berlin, Germany ; |
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Abstract: | Polymerizations of l-lactide catalyzed either by neat SnCl2 or by SnCl2?+?difunctional cocatalysts were conducted in bulk at 180, 160 and 140 °C with variation of the Lac/Cat ratio and time. With neat SnCl2 poly(L-lactide) having weight average molecular weights (uncorrected Mw’s) up to 190 000 g mol?1 were obtained mainly consisting of linear chains. Addition of salicylic acid or 1,1-bisphenol yielded a higher fraction of cyclic polylactides but lower molecular weights. Furthermore, SnCl2 was compared with Bu2SnCl2 and various other metal chlorides and the best results were obtained with SnCl2. With ethyl L-lactate as initiator SnCl2-catalyzed ROPs were performed at 120 °C and the lac/initiator ratio was varied. All these experiments were conducted under conditions allowing for comparison with ROPs catalyzed with neat Sn(II)-2-ethyhexanoate. Such a comparison was also performed with ε-caprolactone as monomer. |
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