Novel hyperbranched poly(amido amine)s containing tertiary amines on the backbones and acryl or secondary amines as the surface groups were successfully synthesized via the Michael addition polymerizations of a triacrylamide [1,3,5-triacryloylhexahydro-1,3,5-triazine (TT)] and a difunctional amine [n-butylamine (BA)] NMR techniques were used to clarify the structures of hyperbranched polymers and polymerization mechanism. The reactivity of the secondary amine formed in situ was much lower than that of the primary amines in BA. When the feed molar ratio was 1:1 TT/BA, the secondary amine formed in situ was almost kept out of the reaction before the BA (AA') and TT (B-3) monomers were consumed, and this led to the formation of A'B-2 intermediates containing one secondary amine group and two acryl groups. The self-polymerization of the A'B-2 intermediates produced hyperbranched polymers bearing acryl as surface groups. For the polymerization with the feed molar ratio of 1:2 TT/BA, A'B-2 intermediates containing one acryl group and two secondary amine groups were accumulated until self-polymerization started; the self-polymerization of the intermediates formed hyperbranched polymers with secondary amines as their surface groups. Modifications of surface functional groups were studied to form new hyperbranched polymers. The hyperbranched poly(amido amine)s were amorphous. (c) 2006 Wiley Periodicals, Inc.