Hydrophilic microporous membranes were prepared via the TIPS process using three hydrophilic ethylene-acrylic acid co-polymers with different co-unit contents and diphenyl ether．These co-polymer were confirmed to the hydrophilic by contact angle measurements．Cloud points were determined visuall by noting the appearance of turbidity under the microscope．The relevant crystallization temperatures for the thermodynamic phase diagram were determined by differential scanning calorimetry (DSC)．The crystallization temperature curves shifted to lower temperatures as the amorphous acrylic acid content of the co-polymer increased．The membrane structures were investigated by scanning electron microscope and related to the initial polymer concentration and acrylic acid content．As the polymer concentration increased or the acrylic acid content decreased

the pore size decreased． However

at the concentration above 50 wt％

the films had no microporosity．