Sulfolane as Common Rate Accelerating Solvent for the Cationic Ring-Opening Polymerization of 2-Oxazolines

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• 作者：Maarten Vergaelen ; Bart Verbraeken ; Bryn D. Monnery ; Richard Hoogenboom
• 刊名：ACS Macro Letters
• 出版年：2015
• 出版时间：August 18, 2015
• 年：2015
• 卷：4
• 期：8
• 页码：825-828
• 全文大小：340K
• ISSN：2161-1653

文摘

The search for alternative solvents for the cationic ring-opening polymerization (CROP) of 2-methyl-2-oxazoline (MeOx) is driven by the poor solubility of P(MeOx) in polymerization solvents such as acetonitrile (CH₃CN) and chlorobenzene as well as in MeOx itself. In this study, solvent screening has revealed that especially sulfolane is a good solvent for PMeOx. Unexpectedly, an increased propagation rate constant (k_p) was found for the CROP of MeOx in sulfolane. Further extended kinetic studies at different temperatures (60鈥?80 掳C), revealed that the acceleration is due to an increase in frequency factor, while the activation energy (E_a) of the reaction is hardly affected. In order to explore the versatility of sulfolane as polymerization solvent for the CROP of 2-oxazolines in general, also the polymerization kinetics of other 2-oxazoline monomers, such as 2-ethyl-2-oxazoline (EtOx) and 2-phenyl-2-oxazoline (PhOx), have been studied, revealing a common acceleration of the CROP of 2-oxazoline monomers in sulfolane. This also enabled more controlled synthesis of PMeOx-block-PPhOx block copolymers that otherwise suffers from solvent incompatibility.