H. Higashimura et al., "Radical-controlled" oxidative polymerization of phenols. Substituent effect of phenol monomers on the reaction rate, POLYM ADV T, 11(8-12), 2000, pp. 733-738
A "radical-controlled" oxidative polymerization of phenols catalyzed by a t
yrosinase model complex, (1,4,7-triisopropyl-1,4,7-triazacyclononane)cop di
chloride, has been achieved. The polymerization of 4-phenoxyphenol regiosel
ectively proceeded to give poly(1,4-phenylene oxide) showing heat-reversibl
e crystallinity with a melting point. For this polymerization, as the steri
c hindrance of substituent of the catalyst ligands increased the selectivit
y for coupling at the p-position became higher. In this work, the substitue
nt effect of phenol monomers on the reaction rate in the "radical-controlle
d" oxidative polymerization was examined. If was found that the steric fact
ors of the phenol substituents, especially those at the o-positions, influe
nced the reaction rates more greatly than the electronic ones. These data s
trongly support the reaction mechanism of "radical-controlled" oxidative po
lymerization, in which the coupling of phenoxy radical species takes place
from phenoxo-copper(II) complex and/or phenoxy radical-copper(I) complex. C
opyright (C) 2000 John Wiley & Sons, Ltd.