Green citrate-based binary diluents for blood oxygenation membranes with high gas permeability

The diluent significantly influences the structure and properties of the oxygenated membrane prepared via thermally induced phase separation (TIPS). With the increasing concern of damage to human body and environment from diluents, non-toxic and environmental-friendly diluents are gradually gaining more attention. In this study, green binary diluents acetyl trioctyl citrate (ATOC) and acetyl tributyl citrate (ATBC) are used to prepare poly-4-methyl-1-pentene (PMP) flat sheet membranes and hollow fiber membranes (HFMs) via TIPS. Firstly, the effects of ATOC/ATBC mass ratio on the morphology, gas permeability, mechanical properties, and crystallization behaviors of flat sheet membranes are investigated. When the ATOC/ATBC mass ratio is 6/4, the membrane has high gas permeability and mechanical properties. Furthermore, the optimal polymer-diluent composition is applied to the preparation of HFMs. The effects of spinning parameters (flow rate of core liquid, and spinning speed) on morphology, gas permeability, and blood oxygenation performance of PMP HFMs are studied. Under optimized preparation conditions, the PMP HFM exhibits high gas permeability (the permeability of O2 is 39.4 +/- 2.1 mL min-1 cm-2 bar- 1 and the permeability of CO2 is 42.3 +/- 2.3 mL min-1 cm-2 bar-1), which is higher than the results reported in previous research. The PMP HFM also shows excellent blood oxygenation performance. This study may contribute to the green preparation of PMP oxygenated membranes for artificial membrane lungs.