Amino modified multiwall carbon nanotubes (MWNTs) are prepared, respectively, by two ways: the conventional one-step method that directly treats acyl chloride functionalized MWNTs with 4, 4-diaminodiphenyl ether (ODA), giving the amino modified MWNT (Di-MWNT), as well as an improved two-step method in which acyl chloride functionalized MWNT react with mono-Boc protected ODA first and then the Boc-groups are deprotected to provide the amino modified MWNT (NH2-MWNT). Anhydride-terminated polyimide (PI) composite films based on NH2-MWNT and Di-MWNT are fabricated by solution blending and consequent planar casting. The exposed amino groups of NH2-MWNT create strong covalent bonds with the anhydride-terminated polyamide acid in the course of N-acylation and curing chemical reactions. Solubility examinations of nanotubes and morphologies of the composite films indicate that the dispersion of NH2-MWNT is significantly better than Di-MWNT in PI matrix and NH2-MWNT can form connected network throughout the PI matrix which makes the NH2-MWNT/PI film presenting superior conductivity. Both morphologies and mechanical properties of the composites show that NH2-MWNT has stronger interfacial interaction with the PI matrix. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3449-3457