A novel microporous membrane was synthesized from a polymeric nano-composite material, mica-intercalated-Nylon 6, by isothermal immersion-precipitation in a pure water bath. This novel membrane was skinless and was composed of cellular pores and sheaf-like crystallites, which interwove into a bi-continuous structure. By contrast, pure Nylon 6 precipitated under the same condition yielded a skinned asymmetric membrane. Differential scanning calorimetry (DSC) analysis of this membrane revealed a slightly higher degree of crystallinity than the nano-composite pellet. In addition, porosity of the membrane was found to increase with increasing water content in the dope. This was evidenced by the tensile strength and the water permeability measurements.