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The grafting of phenol groups on ethylene/5,7‐dimethylocta‐1,6‐diene copolymers and on ethylene/propylene/5,7‐dimethylocta‐1,6‐diene terpolymers was performed, using two different modification procedures. An indirect route involving hydrochlorination followed by phenol insertion was found to be very effective for the terpolymers, and lead to a grafting phenol rate higher than 75%. However, if the phenol grafting is performed directly on a non‐modified terpolymer, lower rates are obtained. When applied to the copolymers the procedures used were revealed to be less efficient. This fact might be related to the lower solubility of the ethylene/5,7‐dimethylocta‐1,6‐diene copolymers (related to a higher crystallinity and a smaller diene content) when compared with the corresponding terpolymers. Although incomplete, the addition of a hindered phenol to the copolymer gave rise to a polymer that, when compared to polyethylene, presents a higher thermal‐oxidative stability.

Polyolefin based materials with chemically bonded phenol compounds have been synthesized. Two unsaturated polyolefins: an ethylene/propylene/5,7‐dimethyl‐1,6‐octadiene terpolymer and an ethylene/5,7‐dimethyl‐1,6‐octadiene copolymer, were used as starting materials. The functionalisation method involves a two‐step procedure that consists in the hydrochlorination of the substituted pending double bonds, followed by grafting of the phenol compound. This procedure was found to be more effective for the terpolymer than for the corresponding copolymer. The reasons for this are discussed. A thermogravimetric study, in air atmosphere shows that, poly(ethylene‐co‐5,7‐dimethyl‐1,6‐octadiene) grafted with 2‐tert‐butyl‐4‐methylphenol present improved thermo‐oxidative stability when compared to a polyethylene reference.