Polypropylene (PP) and polyamide-6 (Ny-6) blends with a 70/30 composition have been studied by broadband dielectric spectroscopy. The unmodified blends are immiscible, and 10% of PP functionalized. with maleic anhydride was added as a compatibilizer. The influence of the compatibilizer on the water sorption and on the molecular dynamics of the Ny-6 phase is followed by the changes induced in the dielectric loss spectra of these blends in both wet and dry states. The shortest range motions are unaffected by the compatibilizer in the dry state, but a higher water sorption is observed in the unmodified blend. Higher activation energies are found for the beta relaxation in the dry blends than for the Ny-6 homopolymer, showing the existence of constraints on these longer scale motions. During increasing temperature experiments, two segmental modes are recorded, the lower temperature mode corresponding to the plasticized material; as the temperature is raised, a second cooperative mode is found, originating in the dry Ny-6 amorphous phase, rigidized by the loss of moisture. The comparison of the dielectric strengths of the modes shows that the unmodified blend absorbs more water than the compatibilized blend. The segmental dynamics are unaffected by compatibilization. At high temperatures, the high temperature tail of the segmental mode is much higher in the absence of the compatibilizer. The contribution of a peak due to interfacial polarization is lowered by the presence of the compatibilizer, which makes the interface more diffuse and the trapping of free carriers less effective. (c) 2005 Wiley Periodicals, Inc.