Permeation properties of copolyimide UF membrane with good thermal stability

Copoly(bis[4-(3-aminophenoxy)phenyl]sulfone/bis(4-aminophenyl)l,4-diisopropylbenzene/pyromellite) imide (COPI) was synthesized using an one-step imidization method. COPI exhibited excellent thermal stability and dissolved well in a number of aprotic polar solvents. COPI was used for the fabrication of membrane materials. COPI ultrafiltration (UF) membranes were prepared using a phase inversion method. Factors influencing the permeation properties and the thermal stability of the membrane were studied. The preparation conditions were determined to be important factors influencing the performance of the membrane. The thermal stability of the membrane was observed by measuring the shrinkage of area and the relative ratio of the permeate flux (J_t)/pure water flux (J₀). The relative flux for the poly(ethylene glycol) (MW 2.0×10⁴) aqueous solution increased from 0.15 to 0.55 when temperature increased from 25 to 90 °C, respectively. The area of the membrane was unchanged under varying temperature. The membranes exhibited good thermal stability and were relatively simple to construct.