Hotta D, Kanazawa A, Aoshima S. tert-Butyl Esters as Potential Reversible Chain Transfer Agents for Concurrent Cationic Vinyl-Addition and Ring-Opening Copolymerization of Vinyl Ethers and Oxiranes.
Macromol Rapid Commun 2020;
42:e2000479. [PMID:
33200479 DOI:
10.1002/marc.202000479]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 09/30/2020] [Indexed: 11/10/2022]
Abstract
tert-Butyl esters are demonstrated to function as chain transfer agents (CTAs) in the cationic copolymerization of vinyl ether (VE) and oxirane via concurrent vinyl-addition and ring-opening mechanisms. In the copolymerization of isopropyl VE and isobutylene oxide (IBO), the IBO-derived propagating species reacts with tert-butyl acetate to generate a copolymer chain with an acetoxy group at the ω-end. This reaction liberates a tert-butyl cation; hence, a polymer chain with a tert-butyl group at the α-end is subsequently generated. Other tert-butyl esters also function as CTAs, and the substituent attached to the carbonyl group affects the chain transfer efficiency. In addition, ethyl acetate does not function as a CTA, which suggests the importance of the liberation of a tert-butyl cation for the chain transfer process. Chain transfer reactions by tert-butyl esters potentially occur reversibly through the reaction of the propagating cation with the ester group at the ω-end of another chain.
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