For improving dispersion of carbon nanotubes (CNTs) in a polymer matrix, multiwalled carbon nanotubes (MWCNTs) were first modified by ring-opening polymerization of the terminal hydroxyl of MWCNTs with epsilon-caprolactone (epsilon-CL). Then, the modified MWCNTs were added into polyurethane (PU) and MWCNTs/PU composite fibers were prepared by electrospinning and collected in the form of membranes. The morphology and microstructure of the composite nanofibers were analyzed by SEM. The relationship between the tensile properties of the membranes and the mass fraction of the MWNTs was revealed by tensile testing. (C) Koninklijke Brill NV, Leiden, 2011