Abstract
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.
At ambient temperature, the combination of Cu(0) or Fe(0) (powder or wire) with TEMPO can readily remove or modify thiocarbonylthio end groups of RAFT polymer at ambient temperature
via
a radical cross coupling/disproportionation mechanism, especially for RAFT-made PMMA.