The compatibilizing efficiency of three different compatibilizers oil the thermoplastic polyurethane/styrene-co-acrylonitrile (TPU/SAN) blends properties was investigated after compatibilizer's incorporation via melt-mixing. The compatibilizers studied were as follows: poly.-caprolactone (PCL) of different molecular weight (M-w), a mixture of polystyrene-block-polycaprolactone (PS-b-IICL) and polystyrene-block-poly (methyl methacrylate) (PS-bPMMA), and a mixture of polyisoprene-block-polycaprolactone (PT-b-PCL) and polybutadiene-block-poly (inethyl methacrylate) (PB-b-PMMA). In our study, the effect of 5 wt % added compatibilizers oil TPU/SAN blends morphology was examined. The transmission electron microscopy (TEM) was used to Study the morphology at different length scales and to determine the compatibilizer's location. Investigations showed the different improvement of properties, because of the different incorporation of compatibilizers in the polymer blend. The morphology influence on the rheological behavior of compatibilized blends was investigated with a stress-controlled rheometer (Rheometric Dynamic Stress Rheometer, SR-500). Different compatibilization activity was found for different system. It was also found that compatibilization activity of added compatibilizer strongly depends oil the comaptibilizer's M-w. Blends compatibilized with PCL showed superior properties as compared with the other examined blends. (c) 2006 Wiley Periodicals, Inc.