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1.
Membranes from polysulfone/N,N-dimethylacetamide/water system
Vladimir Kaiser, Črtomir Stropnik, 2000, original scientific article

Abstract: Polymeric membranes were prepared by the wet-phase separation method from solutions of different contents of polysulfone in N,N-dimethylacetamide; solutions were cast in different thickness before immersion into the pure water coagulation bath. Two main processes take place during the formation of membranes: nucleation and growth of the polymer lean phase with subsequent solidification of the polymer rich phase, and the formation of channels, macrovoids and mega-macrovoids. By the first process a cellular structure is formed whilst the second process connects the cells by opening the space between them. The degree of interconnectedness is an additional factor that affects the pure water flux. By changing the cast solution compositions and/or their cast thickness the interconnectedness of the cells can be controlled.
Keywords: chemical technology, organic technology, polymer membranes, membrane preparation, wet phase inversion, polymers, polysulphon
Published: 18.08.2017; Views: 938; Downloads: 96
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2.
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: 827; Downloads: 84
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4.
Kemijska modifikacija polimernih membran iz polisulfona
Nerina Verko, Črtomir Stropnik, 1994, original scientific article

Published: 10.07.2015; Views: 918; Downloads: 31
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6.
Imobilizacija tripsina na površino membrane iz celuloznega acetata
Andreja Kranjc, Črtomir Stropnik, 1994, original scientific article

Keywords: membrane, prenos snovi, površine, tripsin
Published: 10.07.2015; Views: 744; Downloads: 27
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7.
Polimerne asimetrične porozne membrane
Črtomir Stropnik, 1994, original scientific article

Published: 10.07.2015; Views: 887; Downloads: 32
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8.
Friedel-Crafts-ove reakcije na površini membran iz polisulfona
Nerina Verko, Črtomir Stropnik, 1995, original scientific article

Published: 10.07.2015; Views: 642; Downloads: 30
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9.
Priprava membran iz delno kristaliničnega poliamida 6,6
Ljubo Germič, Leonida Oberš, Vesna Lahovnik, Črtomir Stropnik, 1995, original scientific article

Published: 10.07.2015; Views: 797; Downloads: 30
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10.
Določanje lastnosti tripsina, imobiliziranega na površino membrane iz celuloznega acetata
Andreja Kranjc, Črtomir Stropnik, 1996, original scientific article

Abstract: V prispevku je opisana metoda kovalentne imobilizacije tripsina na površino asimetrične porozne membrane iz celuloznega acetata. Določene so pretočne lastnosti in debeline membrane pred imobilizacijo encima in po njej, aktivnost tripsina v raztopini in lastnosti tripsina v območju pH od 2 do 12.
Keywords: kovalentna imobilizacija tripsina
Published: 10.07.2015; Views: 930; Downloads: 29
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