A gradient extraction method was developed and used for a synthetic leather made of polyurethane (PU) and microfiber polycaprolactam (PA-6), by which the two components were separated using DMF and formic acid as solvents, respectively. Their chemical structure was confirmed by FTIR spectra, and the result showed that the PU is a kind of polyester polyurethane with phenylene rings in the molecule. The condensed phase structure was analyzed using X-ray diffraction (XRD). The crystallinity of the PA-6 is about 65.6%, and for the PU, there was not distinct crystalline character shown in the XRD pattern but a phase separation structure of hard block-soft block with the hard domains content about 58.7%. SEM images showed that the PA-6 micro-fibers transfixing the PU matrix form a net bundle structure, and there are two kinds of porous structures in the synthetic leather, with one type of pore sized 5-80 mu m between the components of PU and PA-6, and the other in PU matrix with a size of 0.1-2 mu m. The multipores run through the synthetic leather as three-dimensional channels, benefit for transportation of air, water, dyes, and so on. (c) 2006 Wiley Periodicals, Inc.