Thermoplastic olefin blends of polypropylene (PP) and ethylene octene copolymers (EC) were reactively compatibilized by means of functional reactive compounds capable of forming copolymers at the interface. For this purpose, amine functional groups were first incorporated into a PP in a solution reaction. The aminated PP was then used as the reactive compatibilizer during melt mixing. Linear viscoelastic measurements showed that the compatibilized blends feature the characteristics of materials in the sol-gel transition, with a power-law behavior for the dynamic moduli at low frequencies. The gel-like behavior was more pronounced in the blend with a high level of compatibilizer (10 wt. %). At high frequencies, however, the dynamic properties of all the blends investigated (compatibilized and noncompatibilized) were identical, suggesting that the bulk properties of the blends were not changed by the reactive compatibilization. The presence of a network structure was also confirmed by microscopic observations. A large transient viscosity with a significant and broad overshoot was observed for the compatibilized blends at low shear rate. In addition, the stress of the compatibilized blends relaxed over a much longer time as compared to the noncompatibilized system. The ability of different linear viscoelastic models in predicting the linear viscoelastic behavior of the compatibilized blends was also examined. (C) 2012 The Society of Rheology. [http://dx.doi.org/10.1122/1.3700966]