Vergaelen Maarten, Verbraeken Bart, Monnery Bryn D, Hoogenboom Richard
Supramolecular Chemistry Group, Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281, S4, Ghent, Belgium.
ACS Macro Lett. 2015 Aug 18;4(8):825-828. doi: 10.1021/acsmacrolett.5b00392. Epub 2015 Jul 20.
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 (CHCN) 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 () was found for the CROP of MeOx in sulfolane. Further extended kinetic studies at different temperatures (60-180 °C), revealed that the acceleration is due to an increase in frequency factor, while the activation energy () 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--PPhOx block copolymers that otherwise suffers from solvent incompatibility.
2-甲基-2-恶唑啉（MeOx）阳离子开环聚合（CROP）的替代溶剂的研究，是由于聚（MeOx）在诸如乙腈（CHCN）和氯苯等聚合溶剂以及MeOx本身中的溶解性较差所驱动的。在本研究中，溶剂筛选表明，环丁砜尤其对聚甲基恶唑啉是一种良好的溶剂。出乎意料的是，在环丁砜中发现MeOx的CROP的增长速率常数（）增加。在不同温度（60 - 180°C）下进一步扩展的动力学研究表明，加速是由于频率因子的增加，而反应的活化能（）几乎不受影响。为了总体上探索环丁砜作为2-恶唑啉CROP聚合溶剂的通用性，还研究了其他2-恶唑啉单体，如2-乙基-2-恶唑啉（EtOx）和2-苯基-2-恶唑啉（PhOx）的聚合动力学，揭示了环丁砜中2-恶唑啉单体CROP的共同加速。这也使得能够更可控地合成聚甲基恶唑啉 - 聚苯基恶唑啉嵌段共聚物，否则该嵌段共聚物会受到溶剂不相容性的影响。
