The objective of this work was to study the interactions between polyamide-6,6 (PA-6,6) and hyper-branched (HB) polyamide with different functional end groups. The investigation focused on the thermal, dielectric, and viscoelastic properties of two kinds of HB polyamides, with amine and alkyl end groups, prepared by a one-pot process, in a polyamide-6,6 matrix. Thermal analysis (by TGA and DSC) allowed us to observe decomposition and glass-transition temperatures of these polymers. The melting point, crystallization temperature, and crystallinity ratio remained practically independent of HB content. Dielectric relaxation spectroscopy (DRS) showed two secondary relaxation (gamma and beta) and one primary (alpha) relaxation in the HB polymers and in the blends similar to those observed in polyamide-6,6 with comparable activation energies and distribution parameters. An increase of the glass-transition temperature was observed, showing a reinforcement of the polymer matrix and a decrease of the molecular mobility of the polyamide chains when the percentage of amine-terminated HB polyamide increased in the matrix. DRS results found on the alkyl-terminated HB polymer blend were indistinct from those of the polyamide-6,6 matrix. Viscoelastic experiments confirmed the results observed in DRS. (c) 2005 Wiley Periodicals, Inc.