The water contact angle was measured at room temperature using a goniometer (Standard Goniometer with DROP image Standard, model 200-00, Ramé-Hart Instrument Co.).The porosity was determined according to Chakrabarty et al.(2008). The cross-sectional morphologies of membranes were examined using scanning electron microscopy (SEM), JEOL equipment, model JSM-6480 LV. The samples were fractured in liquid nitrogen and sputtercoated with gold.