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Single‐Mode Microwave Ovens as New Reaction Devices: Accelerating the Living Polymerization of 2‐Ethyl‐2‐Oxazoline
Authors:Frank Wiesbrock  Richard Hoogenboom  Caroline H Abeln  Ulrich S Schubert
Abstract:Summary: The ring‐opening cationic polymerization of 2‐ethyl‐2‐oxazoline was performed in a single‐mode microwave reactor as the first example of a microwave‐assisted living polymerization. The observed increase in reaction rates by a factor of 350 (6 h → 1 min) in the range from 80 to 190 °C could be attributed solely to a temperature effect as was clearly shown by control experiments and the determined activation energy. Because of the homogenous microwave irradiation, the polymerization could be performed in bulk or with drastically reduced solvent ratios (green chemistry).
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Monomer conversion, represented by the ratio ln{M0]/Mt]}, plotted against time for six temperatures in the range from 80 to 180 °C, and polymerization reaction vials, showing an increase in yellow color for those reactions performed (well) above and below 140 °C, indicating side reactions.

Keywords:activation energy  green chemistry  2‐oxazoline  ring‐opening polymerization  single‐mode microwave system
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