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1.
Chemical modification and characterization of the surface of polysulfone membranes
Irena Kukovičič, Robert Šoster, Milan Brumen, Volker Ribitsch, D. Wiegel, K. Arnold, Črtomir Stropnik, 2000, original scientific article

Abstract: Asymmetric porous membranes were prepared from polysulfone by a wet-phase separation procedure. Different chemical modifications were applied to the upper membrane surface, i.e. the surface which was exposed to interaction with nonsolvent (water) in the coagulation bath during the membrane formation. The membrane surface was modified by the series of Friedel-Crafts electrophilic substitutions of aromatic rings in the polysulfone molecules. As a reagent 1-chlorodecane or propylene oxide dissolved in hexane and $AlCl_3$ as a catalyst were used. In the former case a hydrophobic and in the latter one a hydrophilic coating was achieved, respectively. The membrane surface was also modified by sulfonization with sulfuric (VI) acid water solution; in this way negative charges were introduced at the membrane surface. The membranes, unmodified and chemically modified, were characterized by measuring the membrane thickness, the deionized water flux through the membrane, the zeta potential and contact angle. The specific chemical modifications of the membrane surface affect the water flux, the zeta potential and contact angle values whereas the membrane thickness remains unchanged. These effects are interpreted in terms of hydrophilicity and hydrophobicity, changes of the membrane surface charge and the thickness of shear layer at the membrane surface, all with respect to the particular modification applied. Reaction with 1-chlorodecane gave a hydrophobic surface by nonpolar $–(CH_2)_9-CH_3$ groups and reaction with propylene oxide gave a hydrophilic surface with polar group $-CH(CH_3)-CH_2-OH$. The surface of sulfonized polysulfone membranes contained ionizable ($-SO_3H$) functional groups.
Keywords: polysulfone, chemical modification, Friedel-Crafts electrophilic substitution, sulfonization, hydrophylicity, hydrophobicity
Published: 17.08.2017; Views: 867; Downloads: 86
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2.
Wet-phase-separation membranes from the polysulfone/N,N-dimethylacetamide/water ternary system: the formation and elements of their structure and properties
Črtomir Stropnik, Vladimir Kaiser, Vojko Musil, Milan Brumen, 2005, original scientific article

Abstract: Asymmetric and porous polysulfone (PSf) membranes were prepared by wet phase separation. Binary (PSf)/N,N-dimethylacetamide (DMA) solutions with polymer concentrations of 12.5-30 wt % were cast in thicknesses of 80-700 m and immersed in a coagulation bath of pure water. The morphology of the formed membranesć cross sections consisted of a cellular structure and macrovoidsč the cellular structure density was highest when the cast solution contained about 21 wt % PSf, regardless of the cast thickness. The membranesć pure waterpermeability decreased as the cast thickness increased. The instantaneousonset of the turbidity, regardless of the PSf content and cast thickness, its steep growth, and relatively high end value were the main characteristics of the turbidity phenomena taking place during the formation of the protomembranes. Again, the membrane-forming system with a PSf/DMA solution with about 21 wt % polymer, regardless of the cast thickness, had thehighest turbidity end value. The shrinkage of the cast solutions into the corresponding protomembrane was also examined quantitatively. Inverse experiments showed that the direction of the gravitation field had no influence on the shrinkage of the membrane-forming ternary system or the membranesć morphology and its water permeability.
Keywords: polymeric membranes, polysulfone asymmetric porous membranes, wet-phase separation, membrane preparation, morphology
Published: 01.06.2012; Views: 1496; Downloads: 72
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