Hydrophilic microporous PES membranes prepared by PES/PEG/DMAc casting solutions

Microporous poly(ether sulfones) (PES) membranes were prepared via phase inversion using poly (ethylene glycol) (PEG) as additive and N,N-dimethylacetamide (DMAc) as solvent. Thermodynamic of the casting solutions was studied by coagulation value while precipitation rate was observed by light transmittance measurement. It was found that casting solution with PEG200 as additive was thermodynamically less stable than those with PEG400 and PEG600 as additive and easier to cause phase separation in exposure time. With the increase of PEG200 concentration, the casting solution became thermodynamically less stable and easier to cause phase separation in exposure time, but precipitation rate during immersion precipitation decreased because of the increased viscosities. ATR-FTIR spectra and TGA curves showed that the membranes prepared using PEG200 as additive had less PEG residual than those of PEG400 and PEG600, but it showed better permeation performance than that prepared using PEG400 and PEG600 as additive. With the increase of PEG200 concentration from 30 to 70 wt %, the cross section structure changed from macrovoid to sponge-like, micropores with a mean pore size around 0.1 mu m began to form on the top surface. When the PEG200 concentration is 60 wt %, the pure water flux was 1845 L M 2 h(-1) bar, which is the highest value. As the PEG200 concentration increased from 30 to 60 wt %, the contact angles decreased from 82.1 degrees to 58.2 degrees. As the addition amount of PEG200 increased, the residual PEG made the prepared membranes more hydrophilic. (c) 2007 Wiley Periodicals, Inc.