Single-Site Calcium Initiators for the Controlled Ring-Opening Polymerization of Lactides and Lactones |
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Authors: | Zhong Zhiyuan Schneiderbauer Stefan Dijkstra Pieter J. Westerhausen Matthias Feijen Jan |
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Affiliation: | (1) Department of Polymer Chemistry and Biomaterials and Institute for Biomedical Technology, Faculty of Science and Technology, University of Twente, 217, 7500 AE Enschede, The Netherlands;(2) Department Chemie der Ludwig-Maximilians-Universität, Butenandtstr. 9 (Haus D), 81377 München, Germany |
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Abstract: | Summary Single-site calcium initiators containing chelating tmhd(H-tmhd = 2,2,6,6-tetramethylheptane-33-dione) ligands[(THF)Ca(tmhd)]2[ -N(SiMe3)2]( -tmhd)(2) and[(THF)Ca(tmhd)]2[ -OCH(Me)Ph]( -tmhd)(3) have been synthesized andapplied for the ring-opening polymerization of L-lactide and -caprolactone. Both 2 and3 were highly reactive andpromoted a fast polymerization of L-lactide and -caprolactoneto high monomer conversions under mild conditions (THF as asolvent, room temperature). More importantly, results showedthat the ring-opening polymerizations of lactides and lactonesinitiated by either 3 or2 in the presence of equivalent2-propanol are living, to provide polymers and block copolymersof controlled molecular weights and tailored end-groups. Thepolymerizations were first-order in monomer up to highconversions, in which the insitu initiating system 2/2-propanol revealed no induction periodand much faster polymerization kinetics as compared to3. |
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