The oxidation of extruded polyphenylene ether resin at moderate temper
atures has been shown to obey Arrhenius kinetics with first-order depe
ndence on the hydroxyl endgroups and half-order dependence on oxygen.
In blends, the oxidation is overall second order in uncapped resin. Th
e phenolic endgroup catalyzes the oxidation of the benzylic methyl gro
ups, so capping the resin leads to a much reduced oxidation rate. The
rate of oxidation of the capped commercial resin is approximately the
same as that of pure capped model compounds, showing that other factor
s such as residual catalyst or structural irregularities play only a m
inor role in promoting the oxidation. A mechanism involving attack of
the endgroup phenoxyl radical on the benzylic methyl group is suggeste
d as the first step in the oxidation of the uncapped polymer.