Macromolecular antioxidants via thiol-ene polyaddition and their synergistic effects

Photochemically initiated thiol-ene addition chemistry was used to prepare an aliphatic polythioether, which was applied as a thiosynergist in combination with macromolecular phenolic antioxidants for the thermal oxidative stabilization of polyolefins. Blends with polypropylene showed an extraordinary oxidative stability due to synergistic effects of the polythioether. Furthermore, the synthesis of an “all-in-one” primary and secondary macromolecular antioxidant was reported, with phenolic antioxidants attached to a polythioether backbone. Two different synthetic approaches to incorporate the thioether and the phenolic antioxidant functions into a single macromolecule were investigated, with a post-polymerization approach proving to be superior to a macromonomer approach. The excellent results in OIT measurements in comparison to commercial antioxidants, in particular of the polythioether blends, coupled with their high molecular weights designed to inhibit leaching, makes these macromolecular antioxidants interesting additives for the long-term stabilization of polyolefins in challenging environments.