Poly(L-lactic acid)(PLLA) is a biodegradable polymer derived from renewable resources and has extensive biomedical applications. In recent years, more and more researchers have prepared successfully PLLA membrane for separation and purification using different methods.
In this study, we fabricated PLLA membranes through non-solvent induced phase separation technique. The binary solvent mixture consisting of 1,4-Dioxane and N-methyl-2-pyrrolidone was used as solvent and water was used as non-solvent. The influence of solvent on the structure and performance of PLLA membrane was investigated using various instruments and experiments. The morphology of the fabricated membranes was observed by using a scanning electron microscope. The viscosity of the casting solution was measured by a rotation viscometer. Contact angle was measured on the membrane surface using a video contact angle system . Filtration experiments were carried out at room temperature using a dead-end ultrafiltration cell with a magnetic stirrer.
The membrane morphology was tuned from closed sponge-like structure to paralleled finger-like structure through the systematical variation of solvent composition. Filtration experiments indicated that the pure water flux reached a maximum and the membrane hydraulic resistance reached a minimum when the solvent composition was fixed at a critical value. The membrane prepared from the binary solvent mixture had larger pore size and higher flux than that prepared from single solvent due to the change of the solubility parameter difference between the solvent and PLLA. In addition, the effect of the concentration of PLLA in casting solution and the wet membrane exposure tine in air on the structure and performance of PLLA membrane were also studied respectively. This work demonstrated that a series of membranes with different structure and performance could be prepared by adjusting the solvent ratio of the binary solvent mixture.