A novel engineering plastic polyundecamethylene 2,6-naphthalamide (PA11N) was prepared via a reaction of 2,6-naphthalene dicarboxylic acid and 1,11-undecanediamine through a three-step procedure. The structure of synthesized PA11N was characterized by elemental analysis, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance (H-1-NMR). The thermal behaviors were determined by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The solubility, water-absorbing capacity, and mechanical properties of PA11N have also been investigated. Melting temperature (T-m), glass transition temperature (T-g), and decomposition temperature (T-d) of PA11N are 294, 139, and 493 degrees C, respectively. The results show that the heat resistance and mechanical properties of PA11N are near to those of polynonamethylene terephthalamide, and PA11N is a promising heat-resistant and processable engineering plastic. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 1094-1099, 2010