Ami-ne and alcohol functional dendritic polymers were used as covalent coupling agents for maleic anhydride grafted polyethylene and their efficiency compared with metallic salt and zinc acetate, acting as an ionic coupling agent. The crosslinking reactions in the molten state were carried out at 150 degrees C in an internal mixer and the resulting modified polyethylenes were characterized by dynamic mechanical analysis and Small angle X-ray Scattering. These agents led to efficient coupling and crosslinking. The covalent coupling reactions were conducted in a heterogeneous multiphase system: The kinetics of crosslinking depends on the nature of the coupling agent: at 150 degrees C, the reactions were completed within 5 min. with the amine hyperbranched polymer and 20 min. with the alcohol functionalized dendritic polymer. The zinc acetate forms ionic interactions with the grafted polyethylene in less than I min. Ionic interactions are thermo mechanically reversible; they correspond to electronic density fluctuations evidenced by SAXS. (c) 2007 Wiley Periodicals, Inc.