Effect of Trapping Agent and Polystyrene Chain End Functionality on Radical Trap-Assisted Atom Transfer Radical Coupling

Polymers

Elizabeth M. Carnicom²  Jessica A. Abruzzese²  Yacouba Sidibe²  Kenneth D. Myers²  Eric S. Tillman¹ 

[1] Department of Chemistry, Bucknell University, Lewisburg, PA 17837, USA;

关键词: atom transfer radical polymerization;    polystyrene;    kinetics;    radical trap;   

DOI  :  10.3390/polym6112737

来源: mdpi

【 摘 要 】

Coupling reactions were performed to gauge the effect of the inclusion of a radical trap on the success of coupling reactions of monohalogenated polystyrene (PSX) chains in atom transfer radical coupling (ATRC) type reactions. The effect of both the specific radical trap chosen and the structure of the polymer chain end were evaluated by the extent of dimerization observed in a series of analogous coupling reactions. The commonly used radical trap 2-methyl-2-nitrosopropane (MNP) showed the highest amounts of dimerization for PSX (X = Br, Cl) compared to coupling reactions performed in its absence or with a different radical trap. A dinitroxide coupling agent was also studied with the extent of coupling nearly matching the effectiveness of MNP in RTA (Radical trap-assisted)-ATRC reactions, while N-nitroso and electron rich nitroso coupling agents were the least effective. (2,2,6,6-Tetramethyl-piperin-l-yl)oxyl-capped PS (PS-TEMPO), prepared by NMP, was subjected to a coupling sequence conceptually similar to RTA-ATRC, but dimerization was not observed regardless of the choice of radical trap. Kinetic experiments were performed to observe rate changes on the coupling reaction of PSBr as a result of the inclusion of MNP, with substantial rate enhancements found in the RTA-ATRC coupling sequence compared to traditional ATRC.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.