Grafting of functional maleimides onto oligo- and polyolefins

In this paper the modification of polyolefins, especially polypropylene (PP), with maleimides is discussed. As there are many problems associated with the analysis of the grafting reaction, commercially available squalane and eicosane were used as model compounds for ethylene‐propylene‐copolymer (EPR) and polyethylene (PE). 2,4,6,8‐Tetramethylnonane (TMN) was synthesized as a novel model compound for PP. N‐Phenylmaleimide and maleimido benzoic acid were grafted onto the oligomers in solution using 2,5‐dimethyl‐2,5‐di‐(tert‐butyl‐peroxy)‐3‐hexyne (Luperox 130) as radical initiator. The grafting efficiency was determined by NMR‐, UV‐spectroscopy, gravimetry and gas‐chromatography. The influence of several reaction parameters on homopolymerformation, amount of modified oligomer and grafting efficiency could be elaborated. NMR‐spectroscopy and SEC were used to analyse the nature of the grafts. Grafting yields were almost quantitative using up to more than 10 mol% monomer, but dropped at higher monomer concentrations to about 60%. The amount of modified oligomer could be increased with higher monomer concentrations or reaction temperatures. Grafting of polymers was done by reactive extrusion. Products were analysed by IR‐spectroscopy. Optimal grafting yields could be achieved with 1 wt% monomer and 0.5 wt% peroxide concentration.