Observing 2‐vinylpyridine and 4‐vinylpyridine anions during living anionic polymerization by in situ Raman spectroscopy

• Published in: Journal of Raman spectroscopy Vol. 48; no. 7; pp. 1002 - 1006
• Main Authors: Chen, Xiaoyun, Ke, Iou‐Sheng, Li, Mingqi, Wu, Janet, Rickard, Mark A.
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.07.2017
• Subjects: Anionic polymerization; Anions; Band spectra; Cross-sections; Electronic structure; in situ; Low concentrations; Monomers; Optimization; Polymerization; Raman; Raman spectroscopy; Spectroscopy; Titration; vinylpyridine
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.5146

We report direct evidence of living anions of 2‐vinylpyridine and 4‐vinylpyridine for the first time to the authors' knowledge on the basis of in situ Raman spectral observations during a living anionic polymerization reaction. The former is characterized by a band at 1607 cm−1 and the latter at 1622 cm−1. A titration experiment was carried out by adding multiple aliquots of 4‐vinylpyridine into a solution containing 2‐vinylpyridine anions. Systematic spectral changes for the aforementioned bands provided convincing evidence for such spectral assignments. These assignments are supported by electronic structure calculations of the monomers and anions. Both anions showed large Raman cross sections, which allowed them to be detected at relatively low concentrations. Such Raman bands will enable facile in situ monitoring of the anionic species and thus can be useful for process development and optimization. Copyright © 2017 John Wiley & Sons, Ltd. Direct evidence of living anions of 2‐vinylpyridine and 4‐vinylpyridine was reported during a living anionic polymerization reaction. The former is characterized by a band at 1607 cm−1 and the latter at 1622 cm−1. These assignments are supported by electronic structure calculations of the monomers and anions.