Modification of polysulfone hollow fiber ultrafiltration membranes using hyperbranched polyesters with different molecular weights

Abstract

A series of hyperbranched polyesters (HBPEs) using trimethylolpropane (TMP) as a core were synthesized via an esterification reaction, and the molecular weights of these HBPEs were 1600, 2260, 3370, and 5170 g/mol, respectively. Then, these HBPEs were added into dope solutions to prepare PSf hollow fiber membranes via a wet‐spinning method. When the HBPE molecule weight increased from 1600 to 5170 g/mol, the initial viscosities of the PSf–HBPE–PEG400–DMAc dope solutions increased, and the shear‐thinning phenomenon of these dope solutions became increasingly obvious. When these dope solutions were immersed into the deionized water, the demixing rate increased with an increase in the HBPE molecule weight at first and then decreased; this results in the increase of membrane porosity and the coexistence of finger‐like and sponge‐like structures. With the addition of HBPE, the start pure water contact angle and the mean effective pore size of the membranes decreased, and the Jw increased. For the mechanical properties of the membranes, the breaking strength and the elongation of the membranes also increased. Copyright © 2015 John Wiley & Sons, Ltd.