A kind of novel aromatic amine bis(4-nonyl-2,5-diamine-penoxyl)alkylate (RA(n)) as curing agents for epoxy resins were prepared through three steps of reactions using nonyl phenol and dibromoalkylate as materials. Dynamic mechanical analysis (DMA) indicated that the secondary relaxation for the resins cured by RA(n) were generated by the nonyls in RA(n) molecules when temperature was below -50 degrees C. Comparing with other reference resins, the enhancement for toughness of RA(n) cured-resins were at least 15%, which were contributed by such secondary relaxation. Furthermore, stiffness of the networks and thermal properties of the resins were not influent by the flexible groups (nonyl) in RA(n) after curing, since the groups were located only in the branched chains of the networks. The mechanical and thermal properties of the new material have been significantly enhanced. The relevant method and procedure developed through this research have been granted Chinese patent recently (Yang and Gong, Chin. Pat. CN1978483A, 2007). (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2706-2710, 2009