Ring‐opening polymerization of ε‐caprolactone catalyzed by Yttrium trisphenolate in the presence of 1,2‐propanediol. Do both primary and secondary hydroxyl groups initiate polymerization? |
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| Authors: | Jun Ling Jinzhi Liu Zhiquan Shen Thieo E Hogen‐Esch |
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| Institution: | 1. MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, China;2. Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089‐1661;3. Jiangsu Research Institute of Building Science Co. LTD, Nanjing 210008, China |
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| Abstract: | Although the ring‐opening polymerization (ROP) of ε‐caprolactone (CL) in toluene at 100 °C can be initiated by yttrium trisphenolate (Y(OC6H5)3), in the presence of 1,2‐propanediol (PD) the ROP gives much better, that is, controlled polymerizations. In this case, the molecular weights (MWs) are controlled by the CL/PD molar ratios with primary and secondary hydroxyl groups both initiating the ROP and the MW distributions are narrow. The chain transfers between the active yttrium alkoxides and the residual hydroxyl groups on the PD and/or the chain ends appear to be much faster than chain propagation, consistent with the living character of the ROP. Computational studies support these facile reactions with estimated activation free energies in the 3.0–4.5 kcal/mol range compared with about 25–30 kcal/mol for the polymerization. Intramolecular transfer within the PD is predicted to be negligible having a calculated activation energy of 19 kcal /mol. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 |
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| Keywords: | catalysis ε ‐caprolactone density functional theory polymerization mechanism quantum chemistry ring‐opening polymerization |
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