Incorporation of Antioxidant Groups into Polydienes. II. Via Free-Radical Reactions of Phenol- or Amine-Substituted Sulfur Compounds

Methods for incorporation of effective antioxidant groups into both emulsion diene homo- or copolymers and stereospecific diene homopolymers via free radical reactions of sulfur-containing compounds were described. They involved either chain transfer reactions of phenol- or amine-substituted mercaptans or disulfides in emulsion diene polymerization systems or free-radical additions of phenol- or amine-substituted alkyl mercaptans to polydienes after polymerization. The latter reactions were applicable both to polydiene latexes and to solutions of stereospecific polydienes. The potential effectiveness of certain phenol- or amine-substituted mercaptans and disulfides to interact with polymer radicals was determined by measurement of chain transfer constants in bulk styrene polymerization. The efficiency of conferment of antioxidant activity upon polydienes by sulfur-containing compounds via chain transfer or addition reactions was determined by oxygen absorption studies of preextracted polymers. In some instances the relationship between the degree of oxidation resistance conferred upon a polymer with its concentration of chemically bound antioxidant function was determined by colorimetric or uv spectrophotometric analysis.