H-Bonding Organocatalysts for Ring-Opening Polymerization at Elevated Temperatures
| Autor: | Matthew K. Kiesewetter, Kurt V. Fastnacht, Danielle N. Coderre, Thomas J. Wright, Nayanthara U. Dharmaratne |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Lactide
Polymers and Plastics Organic Chemistry Thio 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Ring-opening polymerization Toluene Decomposition 0104 chemical sciences Catalysis Inorganic Chemistry Solvent chemistry.chemical_compound chemistry Polymerization Polymer chemistry Materials Chemistry 0210 nano-technology |
| Zdroj: | Macromolecules. 51:10121-10126 |
| ISSN: | 1520-5835 0024-9297 |
| DOI: | 10.1021/acs.macromol.8b02219 |
| Popis: | The ring-opening polymerization (ROP) kinetics of e-caprolactone and lactide with various H-bonding organocatalysts, (thio)ureas paired with an amine cocatalyst, were evaluated at temperatures up to 110 °C. In nonpolar solvent, most cocatalyst systems exhibit decomposition at high temperatures, while only two, a monourea and bis-urea H-bond donor plus base cocatalyst, are stable up to 110 °C. The onset temperature of cocatalyst decomposition must be measured under reaction conditions. In polar solvent, when the more active imidate form of the (thio)urea is favored, most cocatalyst systems become thermally stable up to 110 °C, exhibiting linear Eyring behavior, including some that were unstable in toluene. The very progress of an ROP is shown to influence the nature of the catalysts as the solution polarity changes from highly polar (at 0% conversion) to less polar at full conversion. Activation parameters are discussed, and a mechanistic explanation of the observations is proposed. |
| Databáze: | OpenAIRE |
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