Application of surface modifying macromolecules in polyethersulfone membranes: Influence on PES surface chemistry and physical properties

Novel surface modifying macromolecules (SMMs) were developed for incorporat ion into polyethersulfone (PES) membranes, intended for pervaporation appli cations. These materials were synthesized with a diisocyanate, polypropylen e oxide (PPO), and a fluoro-alcohol, and characterized for elemental analys is, molecular weight, and glass transition temperatures. PES/SMM blends wit h eight types of SMMs were characterized for surface and physical propertie s and compared with PES. Water droplet contact angle measurements and X-ray photoelectron spectroscopy data showed that the SMMs migrated to the surfa ce and rendered the PES material more hydrophobic. While advancing contact angle data were equivalent to those of pure Teflon(TM) the highest average values of receding angles of these systems were less than those commercial Teflon(TM). The opaqueness of PES/SMMs films and data from differential sca nning calorimetry experiments showed that the SMMs were either immiscible o r only partially miscible with PES. It was also observed, for a fixed PES c oncentration of 25 wt %, that increases in the molecular weight of the SMMs and the weight fraction of PPO in the SMMs led to phase separation in the ternary PES/SMMs/dimethylacetamide (i.e., membrane casting solution) system . On the other hand, in the binary PES/SMMs system (i.e., cast membrane fil m), an increasing weight fraction of fluorine in the SMMs contributed to an increase in the phase separation. (C) 1999 John Wiley & Sons, Inc.