Oxidation reactions are one of the main reasons for the failure of polymeri
c materials. Antioxidants, compounds designed to protect against oxidation,
must meet three main requirements for success: (1) an efficient antioxidat
ive mechanism, (2) compatibility with the oxidizing polymer, and (3) perman
ence within the oxidizing polymer. Common antioxidants are low molecular we
ight materials that can easily diffuse, leach, or evaporate from the polyme
r they are designed to protect. An increase in the molecular weight of the
antioxidant not only decreases diffusion and volatility, but also decreases
compatibility since most high molecular weight polymers will not mix. Sele
ctive sterically hindered phenolics, however, are concurrently antioxidants
and "compatibilizers" through hydrogen bond formation. Carefully designed
copolymers containing a small percentage of 2,6-diisopropyl-4-vinylphenol w
ere found to mix intimately with two readily oxidizing polyethers and to pr
otect them against oxidation.