A flexible hyperbranched aromatic polyamide-imide (PAI) having an amine group in the center and carboxyl groups in the ends was synthesized from a AB(2) type of monomer of 2-(6-aminohexylcarbomoyl) terephthalic acid that was prepared from trimellitic anhydride and 1,6-diaminohexane. Fourier transformed infrared spectra (FTIR), NMR, and ES-MS were used to characterize the structure of the monomer and the synthesized hyperbranched polymer. Then the hyperbranched PAI was grafted onto the multiwalled carbon nanotubes (MWNTs) that was first treated by acid and changed into MWNT-COCI by SOCl2 in a tetrahydrofuran solution. By observation with transmission electron microscopy and characterization with FTIR and thermal gravity of analysis, the functionalized MWNTs were terminally enclosed with polymer; it was believed that the MWNTs were linked with a big carboxylic claw at the end and the adsorption ability of the MWNTs to NH2-Substrate was enhanced. (c) 2007 Wiley Periodicals.