R–Cl/SnCl 4 / n -Bu 4 NCl-induced direct living cationic polymerization of naturally-derived unprotected 4-vinylphenol, 4-vinylguaiacol, and 4-vinylcatechol in CH 3 CN

• Published in: Polymer chemistry 2019-03, Vol.10 (10), p.1192-1201
• Main Authors: Takeshima, Hisaaki, Satoh, Kotaro, Kamigaito, Masami
• Format: Article
• Language: English
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/C8PY01831F

A combination of an alkyl chloride (R–Cl) as an initiator and MtCl n as an activator, which is a common initiating system for living cationic polymerizations, was used for the direct cationic polymerization of unprotected 4-vinylphenol or p -hydroxystyrene (pHOS), which were derived from naturally-occurring p -coumaric acid via decarboxylation, in the absence and presence of additives such as n -Bu 4 NCl. The initiating system consisting of an HCl-adduct of p -methoxystyrene (pMOS–HCl), SnCl 4 , and n -Bu 4 NCl induced the direct living cationic polymerization of pHOS in CH 3 CN at −40 °C without using any protective groups on the phenolic groups and resulted in well-defined poly(pHOS) with controlled molecular weights and narrow molecular weight distributions (MWDs) ( M w / M n = 1.1–1.2). The pMOS–HCl/SnCl 4 / n -Bu 4 NCl initiating system was also effective for living cationic polymerization of pMOS in CH 3 CN even in the presence of phenol, where side reactions such as proton initiation and chain-transfer reactions caused by phenol were almost completely suppressed. 1 H and 119 Sn NMR analyses of the mixtures revealed that CH 3 CN strongly interacted with both the phenol and SnCl 4 and thereby prevented the direct interaction between the phenol and SnCl 4 , suppressing these side reactions. Similar direct living cationic polymerizations of 4-vinylguaiacol and 4-vinylcatechol, which were obtained via decarboxylation of naturally-occurring ferulic and caffeic acids, respectively, resulted in well-defined polymers ( M w / M n = 1.1–1.2) in CH 3 CN without protecting the phenol and catechol groups.