A novel tunable polypropylene hollow fiber membrane with gradient structure for extracorporeal membrane oxygenation applications

High gas permeability and excellent resistance to plasma leakage are expected from polypropylene (PP) hollow fiber membranes (HFMs) used in extracorporeal membrane oxygenation (ECMO) systems. This study successfully prepared a novel PP HFMs with tunable and gradient structures using oleic acid (OA) and methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (RhodiasolvⓇ PolarClean) (PL) as binary diluents via the hybrid induced phase separation (HIPS) method. The phase-separation behavior of the PP-OA/PL system was studied using a phase diagram and the resultant membrane structure. As the concentration of PL in the binary diluents increased, the phase separation mechanism changed from solid–liquid (S–L) to liquid–liquid (L–L), and the structure of PP HFMs changed from crystalline to cellular or bi-continuous. Moreover, the effects of PP concentration and air gap distance on the membrane structure and performance were investigated. In particular, the obtained HFMs showed a clear gradient configuration. The results showed that when the PP concentration, OA to PL mass ratio, and air gap were set to 35 wt%, 7/3, and 10 mm, respectively, the PP HFM exhibited the optimal performance with a high N2 permeability of 23.42 ± 0.98 ml/(min cm2 bar) and resistance to simulated plasma leakage of 4300 min.