Zero-valent metal catalyzed radical-induced adjustable removal/modification of thiocarbonylthio end groups of RAFT polymer at ambient temperature†
Xiaofei Zhanga, Wenxiang Wanga, Kai Guob, Chrys Wesdemiotisbc, Zhengbiao Zhang*a (张正彪) and Xiulin Zhu*a (朱秀林)
aJiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Department of Polymer Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China. bDepartment of Polymer Science, The University of Akron, Akron, Ohio 44325, USA. cDepartment of Chemistry, The University of Akron, Akron, Ohio 44325, USA
Polym. Chem. 2013, 4, 637-644.
This work describes a facile removal/modification of thiocarbonylthio end groups of RAFT-made polymers by the utilization of zero-valent copper (Cu(0)) powder/2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) under mild conditions, especially for poly(methyl methacrylate) (PMMA). At [PMMA]0/[Cu(0)]0/[ligand]0/[TEMPO]0 = 1/5/5/1.5, the molecular weights (MWs) gradually increased to twofold that of the precursor, due to the polymeric radical–polymeric radical cross coupling. While the MW remained unchanged at [PMMA]0/[Cu(0)]0/[ligand]0/[TEMPO]0 = 1/5/5/5, generating vinyl group terminated telechelic polymers via a polymeric radical–TEMPO disproportionation process. The utilization of Cu(0) wire can also remove the thiocarbonylthio end group effectively. Zero-valent iron (Fe(0)) (powder or wire) can be applied to remove/modify the thiocarbonylthio end group instead of Cu(0)/ligand with comparable results. This work provided an alternative and promising approach for an adjustable end group removal/modification of RAFT polymers, and would eventually strengthen and facilitate the potential large-scale application of RAFT-related polymers.