Hindered Amine Light Stabilizers (HALS) are know to inhibit the photo-
oxidation of polymers. A key reaction in their stabilization mechanism
is believed to be the conversion of a hindered aminoether into a nitr
oxyl radical. Several different possible mechanisms for this conversio
n were explored. One, the elimination of the aminoether to form an ole
fin and hydroxylamine (an intermediate in the formation of a nitroxyl)
, while possible at high temperatures, cannot account for the inhibito
ry activity we observed for secondary and primary aminoethers. Direct
radical displacement by peroxy radicals was also considered. However,
the products predicted by this reaction pathway were not observed. Fin
ally, oxidation of the nitrogen by a peroxy radical, by either electro
n transfer or a radical attack on the nitrogen, was investigated. Whil
e electron transfer was shown to be unlikely, direct oxidation of the
aminoether nitrogen was supported by our results. A detailed mechanism
for the reaction of both alkyl- and acyl-peroxy radicals with aminoet
hers is proposed.