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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, izvirni znanstveni članek

Opis: 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.
Ključne besede: polysulfone, chemical modification, Friedel-Crafts electrophilic substitution, sulfonization, hydrophylicity, hydrophobicity
Objavljeno: 17.08.2017; Ogledov: 49; Prenosov: 0
.pdf Polno besedilo (82,15 KB)

2.
Zeta potencial PA 6
Robert Šoster, Nika Veronovski, Lidija Tušek, Karin Stana-Kleinschek, Simona Strnad, Volker Ribitsch, 2003, izvirni znanstveni članek

Opis: V raziskavi smo preučevali elektrokinetične lastnosti poliamida 6 v obliki (a) folije in (b) tekstilnega filamenta ob uporabi dveh merilnih celic. Merili smo potencial zaradi pretoka in iz tega določili zeta potencial (▫$\zeta$▫ v odvisnosti od pH vrednosti medija. Meritve na posameznem materialu smo preučevali s stališča ponovljivosti. S tem namenom smo opravili meritve na 10 preskušancih istega vzorca. Določili smo osnovne statistične pokazatelje ponovljivosti za ▫$\zeta$▫ pri pH 3 in 9 ter izoelektrično tocko. Metodo smo optimirali glede na čas nabrekanja v raztopini elektrolita pred meritvijo in maso materiala v cilindrični celici. Meritve v 0,001 M KCl na obeh vrstah materiala kljub različni nadmolekulski in površinski strukturi dobro sovpadajo. Krivulje ▫$\zeta$▫=▫$\zeta$▫(pH) imajo pričakovan potek. PA 6 kaže amfoterno naravo zaradi vsebnosti amino in karboksilnih skupin. V alkalnem mediju disociirajo karboksilne skupine, kar povzroči negativen ▫$\zeta$▫ (folija: (-32,9▫$\pm$▫ 1,6) mV, filament: (-35,2▫$\pm$▫2,0) mV pri pH 9). V kislem mediju kaže PA kationski značaj zaradi disociacije amino skupin (folija: (24,5▫$\pm$▫1,7) mV, filament: (15,1▫$\pm$▫1,1) mV pri pH 3). Izoelektrična točka, kjer je ▫$\zeta$▫ enak 0, se nahaja za folijo pri pH vrednosti 4,7▫$\pm$▫0,1, za filament pa pri 4,9▫$\pm$▫ 0,1.
Ključne besede: polimeri, poliamid 6, elektrokinetične lastnosti, potencial zaradi pretoka, zeta potencial, filament, folija
Objavljeno: 01.09.2017; Ogledov: 47; Prenosov: 2
.pdf Polno besedilo (420,18 KB)

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