PDLA/PLLA ultrafiltration membrane with excellent permeability, rejection and fouling resistance via stereocomplexation

In this work, a feasible and efficient approach was developed to produce Poly(lactic acid (PLA) ultrafiltration membrane with both high permeability and high rejection simultaneously. Poly(L-lactic acid)/Poly(D-lactic acid) (PDLA/PLLA) stereocomplex crystallites were thought to play the critical role different from the traditional pore forming agents or hydrophilic modification. The membrane morphology of the stereocomplex PDLA/PLLA membrane with high porosity and thin skin layer was observed by SEM. The addition of PDLA resulted in the thermodynamic enhancement for phase separation of PLLA casting solution as demonstrated by a rotational rheometer. The PDLA/PLLA stereocomplex crystallization behavior was investigated by DSC and XRD. With increasing the stereocomplex crystallites, the water permeability of PLA membrane significantly increased from similar to 482 L/m(2).h to similar to 3325 L/m(2) h, while with small loss in degree of rejection. Furthermore, the stereocomplex PLA membrane demonstrated the excellent separation efficiency for nano-TiO2 and ink dispersion. Besides, the stereocomplex PLA membrane exhibited outstanding anti-protein fouling properties through the static and dynamic BSA antifouling tests. All results demonstrated that the stereocomplexation can effectively tune the pore size evolution and control the permeability, selectivity and fouling resistance.