Fabrication of high performance polyethersulfone UF hollow fiber membranes using amphiphilic Pluronic block copolymers as pore-forming additives

Abstract

The amphiphilic Pluronic triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) have received much attention recently as both the surface modifier and pore former in membrane fabrication. In this study, a systematical study has been carried out to investigate the effect of Pluronics with different molecular architectures and contents as a pore-forming additive on the fabrication of polyethersulfone (PES) ultrafiltration (UF) hollow fibers, and to identify the most preferential features of Pluronic for making high performance membranes. The as-spun hollow fibers were characterized in terms of cross-sectional membrane morphology, membrane surface chemistry, mechanical properties, pure water permeation (PWP), molecular weight cut-off (MWCO), and pore size distribution. It was observed that the PWP and MWCO of the as-spun hollow fibers are dependent on the structure of additives. Among all the membranes spun with 5 wt% additives, the hollow fibers spun using Pluronic F127 and F108 as the additives possess the highest PWP, the lowest MWCO, and the narrowest pore size distribution. It is possible that the PEO brush layer formed on the internal pore surface by Pluronic F127 and F108 might reduce the apparent pore size and hence improved the solute rejection of the resultant membranes. A comparison between Pluronic and poly(ethylene glycol) (PEG) as additives also confirmed the importance of the presence of PPO chain in Pluronic in the formation of high-performance membranes. When Pluronic F127 concentration was 10 wt%, the as-spun hollow fiber exhibited the highest PWP of 113.8 L/m 2 h bar and the lowest MWCO of 9 kDa.