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Poly(styrene-co-divinylbenzene-co-2-ethylhexyl)acrilate membranes with interconnected macroporous structure
Urška Sevšek, Silvo Seifried, Črtomir Stropnik, Irena Pulko, Peter Krajnc, 2011, izvirni znanstveni članek

Opis: A combination of doctor blading and emulsion templating was used to prepare macroporous poly(styrene-co-divinylbenzene-co-2-ethylhexylacrylate) and poly(styrene-co-divinylbenzene) membranes with an interconnected porous structure. Water in oil high internal phase emulsions including monomers in the oil phase were cast onto a glass plate and polymerised at elevated temperature. After purification porous polyHIPE membranes were obtained. The volume ratio of aqueous phase (75 % or 85 %) and the molar ratio of divinylbenzene (2 % or 4 %) were varied, while the addition of chlorobenzene to the oil phase influenced the viscosity of the emulsions. A comonomer, 2-ethylhexylacrylate substantially improved the flexibility of the membranes. All yielding membranes were characterized by measuring their cast thicknesses and flow densities for deionised water. Scanning electron microscopy was used to study the morphological features of the membranes.
Ključne besede: membrane, porous polymers, polyHIPE, emulsions
Objavljeno: 10.07.2015; Ogledov: 1327; Prenosov: 121
.pdf Celotno besedilo (668,83 KB)
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Aryl acrylate based high-internal-phase emulsions as precursors for reactive monolithic polymer supports
Peter Krajnc, Dejan Štefanec, Jane F. Brown, Neil R. Cameron, 2005, izvirni znanstveni članek

Opis: Water-in-oil high-internal-phase emulsions (HIPEs), containing 4-nitrophenyl acrylate and 2,4,6-trichlorophenyl acrylate as reactive monomers, were prepared and polymerized, and highly porous monolithic materials resulted. The novel materials were studied by combustion analysis, Fourier transform infrared spectroscopy scanning electron microscopy, mercury porosimetry, and N2 adsorption/desorption analysis. With both esters, cellular macroporous monolithic polymers were obtained: the use of 4-nitrophenyl acrylate resulted in a cellular material with void diameters between 3 and 7 m and approximately3-m interconnects, whereas the use of 2,4,6-trichlorophenyl acrylate yielded a foam with void diameters between 2 and 5 m, most interconnects being around 1 m. The resulting monoliths proved to be very reactive toward nucleophiles, and possibilities of functionalizing the novel polymer supports were demonstrated via reactions with amines bearing additional functional groups and via the synthesis of an acid chloride derivative. Tris(hydroxymethyl)aminomethane and tris(2-aminoethyl)amine derivatives were obtained. The hydrolysis of 4-nitrophenylacrylate removed thenitrophenyl group, yielding a monolithic acrylic acid polymer. Furthermore,functionalization to immobilized acid chloride was performed very efficiently, with more than 95% of the acid groups reacting. The measurement of the nitrogen content in 4-nitrophenyl acrylate poly(HIPE)s after various times of hydrolysis showed the influence of the total pore volume of the monolithic polymers on the velocity of the reaction, which was faster with themore porous polymer.
Ključne besede: organic chemistry, macroporous polymers, monolithic polymer supports, emulsion polymerisation, foams, functionalization of polymers, high-internal-phase emulsions
Objavljeno: 01.06.2012; Ogledov: 1426; Prenosov: 75
URL Povezava na celotno besedilo

Phenols, proanthocyanidins, flavones and flavonols in some plant materials and their antioxidant activities
Mojca Škerget, Petra Kotnik, Majda Hadolin Kolar, Andreja Rižner Hraš, Marjana Simonič, Željko Knez, 2005, izvirni znanstveni članek

Opis: Methanol extracts prepared from five plant materials native to the Mediterranean area, namely olive tree (Olea europaea) leaf, St. John's wort (Hypericum perforatum), hawthorn (Crataegus laevigata), oregano (Origanum vulgare) and laurel leaf (Lauris nobilis), were examined for their phenolic components. Total phenolic content was determined by the Folin-Ciocalteu method. The content of proanthocyanidins in acid-hydrolysed extracts was determined spectrophotometrically. The contents of free flavones (apigenin andluteolin) and flavonols (kaempferol, myricetin and quercetin) were determined by HPLC analysis. The time of hydrolysis of flavones, flavonols andproanthocyanidins was optimised. Antioxidant activities of apigenin, luteolin, kaempferol, myricetin, quercetin and of plant extracts were examined. Antioxidative activities were studied in sunflower oil at 98 °C, by measuring peroxide value, and in an aqueous emulsion system of -carotene and linoleic acid by measuring the absorbance of the sample. Among flavones and flavonols investigated, only myricetin inhibited oxidation of sunflower oil. All other flavones and flavonols showed pro-oxidative activity. Oppositely, in the emulsion system, only apigenin showed pro-oxidative activity while otherflavones and flavonols and plant extracts inhibited oxidation of -carotene.
Ključne besede: chemical processing, extraction, plant material, fenolic content, hidrolysis, antioxidants, flavones, flavonols, proanthocyanidines, oils, emulsions
Objavljeno: 01.06.2012; Ogledov: 1675; Prenosov: 89
URL Povezava na celotno besedilo

4-vinylbenzyl chloride based porous spherical polymer supports derived from water-in-oil-in-water emulsion
Dejan Štefanec, Peter Krajnc, 2005, izvirni znanstveni članek

Opis: 4-Vinylbenzyl chloride (VBC) based water-in-oil-in-water emulsions with 85% pore volume and 70% VBC in organic phase were prepared and polymerised by free radical polymerisation. Porous spherical particles of diameters between 50 and 150 m were obtained and their morphological structure and reactivity studied by FTIR spectroscopy, elemental analysis, optical microscopy, scanning electron microscopy and mercury intrusion porosimetry. Strong influence of the suspension stabiliser, namely poly(N-vinylpyrrolidone) (PVP), on the particle form was found. Diameters of spherical polymers particles depend on the PVP concentration, being larger with the lower concentration of PVP. Reactivity of novel supports was demonstrated by the reactions with piperidine, piperazine, tris(hydroxymethyl)methylamine and tris(2-aminoethyl)amine, all yielding corresponding amine derivatives.
Ključne besede: multiple emulsions, polymer supports, 4-vinylbenzyl chloride, solid phase synthesis, solid phase synthesis, high internal phase emulsions
Objavljeno: 01.06.2012; Ogledov: 1429; Prenosov: 17
URL Povezava na celotno besedilo

Highly porous open-cellular monoliths from 2-hydroxyethyl methacrylate based high internal phase emulsions (HIPEs) : preparation and void size tuning
Sebastijan Kovačič, Dejan Štefanec, Peter Krajnc, 2007, izvirni znanstveni članek

Opis: Preparation of highly porous (up to 80% pore volume) open-cellular monolithic cross-linked polymers from 2-hydroxyethyl methacrylate is reported. Oil-in-water and water-in-oil high internal phase emulsions are applied as porosity templates, resulting in an interconnected porous structure with void diameters between 550 nm and 18 m. Significantly larger voids were obtained inthe case of oil-in-water emulsions (between 5 and 18 m) as opposed to water in oil emulsions (approx 600 nm). Controlled coarsening exploiting limited kinetical stability of emulsions was used to obtain monoliths with larger voids, diameters being enlarged 3-fold.
Ključne besede: organic chemistry, polymerization, monolithic polymers, HIPE, emulsions, porous materials, methacrylates
Objavljeno: 31.05.2012; Ogledov: 1663; Prenosov: 54
URL Povezava na celotno besedilo

Aryl acrylate porous functional polymer supports from water-in-oil-in-water multiple emulsions
Dejan Štefanec, Peter Krajnc, 2007, izvirni znanstveni članek

Opis: Porous functional polymer supports are a class of material of wide interest due to the possibility of immobilising reactive species. A simplified procedure was applied for the preparation of porous polymer supports using a water-in-oil-in-water multiple emulsion. The primary emulsion was a high internal phase emulsion, having a volume fraction of water phase up to 95%. Two reactive acrylates, namely 4-nitrophenyl acrylate and 2,4,6-trichlorophenyl acrylate, were (separately) incorporated in the oil phase in order to obtain porous reactive polymer supports. Both acrylates were crosslinked with either divinylbenzene or ethylene glycol dimethacrylate, and beads of size ca 60 m were obtained after the polymerisation of droplets suspended into the secondary aqueous phase. In the case of 4-nitrophenyl acrylate and divinylbenzene as a crosslinker, particles with a star shape, the core being ca 60 m in diameter and the arms ca 180 m in length, were obtained. The polymers were functionalised with morpholine, tris(2-aminoethyl)amine, piperidine or piperazine yielding supports with loadings of reactive groups of between 2.6 and 6.6 mmol g-1. The results show that multiple emulsions can be precursors for porous polymer preparation.
Ključne besede: multiple emulzije, polimerni nosilci, HIPE, organska sinteza na trdni fazi, polimerni lovilci, emulzija z visokim deležem notranje faze, aril akrilati, multiple emulsions, polymer supports, HIPE, solid phase organic synthesis, polymer supported scavengers, high internal phase emulsions, arylacrylates
Objavljeno: 31.05.2012; Ogledov: 1859; Prenosov: 94
URL Povezava na celotno besedilo

Sebastijan Kovačič, 2011, doktorska disertacija

Opis: A new class of polyHIPE materials has been prepared using high internal phase emulsions (HIPEs) with monomers in both phases. Resulting materials, namely hybrid polyHIPE materials, are obtained consisting of hydrophobic matrix (consisted of styrene cross-linked with DVB or dicyclopentadiene) filled with hydrophilic polymer gel (polyacrylic acid or polyNIPAM) and exhibit morphology changes according to pH and temperature of the surrounding medium. Our focus with regards to the production of hybrid polyHIPE materials was the responsiveness of such materials used for flow control. This property is beneficial for controlling the flow of the solution through the monolithic polymers. Furthermore, polyHIPE materials have also been prepared by using ring opening metathesis polymerisation of monomers, such as dicyclopentadiene and norbornene. Obtained materials have Young’s moduli in the range of hundred times higher than standard polyHIPE materials with the same level of porosity which represents a very important improvement in the development of highly porous cellular polymeric materials.
Ključne besede: emulsions, high internal phase emulsions, polymers, polyHIPEs, hybrid, hybrid polyHIPE materials, ROMP, flow-through, styrene, DVB, acrylic acid, NIPAM
Objavljeno: 04.05.2011; Ogledov: 2547; Prenosov: 224
.pdf Celotno besedilo (3,71 MB)

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