Styrene and maleic anhydride (MAn) were successfully grafted, alone and simultaneously, onto various model hydrocarbon substrates at 180 degrees C with 2,5-dimethyl-2,5-di-(t-butyl peroxy)hexane (L101) as a free-radical initiator. Dodecane, 1-dodecene, and 2,6,10,14-tetramethyIpentadecane were selected as model compounds to investigate the effects of terminal unsaturation and branching on grafting and crosslinking. These compounds were chosen to mimic the aforementioned microstructural characteristics that are commonly observed in polyethylene. The results demonstrate that terminal unsaturation increases the amount of crosslinked material in the presence of L101. With respect to grafting, for the single monomer systems, MAn prefers to graft as single saturated units, whereas styrene prefers to graft as long chains of polystyrene oligomers. However, when both monomers are grafted simultaneously, graft yields are drastically reduced because of a propensity for the two monomers to form a styrene-maleic anhydride copolymer.