1. Use of emulsion-templated, highly porous polyelectrolytes for in vitro germination of chickpea embryos : a new substrate for soilless cultivationJanja Majer Kovačič, Terezija Ciringer, Jana Ambrožič-Dolinšek, Sebastijan Kovačič, 2022, original scientific article Abstract: The application of highly porous and 3D interconnected microcellular polyelectrolyte polyHIPE (PE-PH) monoliths based on (3-acrylamidopropyl)-trimethylammonium chloride as soilless cultivation substrates for in vitro embryo culture is discussed. The embryo axes isolated from chickpea seeds are inoculated onto the surface of the monoliths and allowed to germinate. Germination study show that the newly disclosed PE-PH substrate performs much better than the conventionally used agar as the germination percentage, shoot and root length, fresh and dry weight as well as the number of leaves are enhanced. The PE-PHs exhibit a higher absorption capacity of the plant growth medium, that is, 36 g·g–1 compared to agar, that is, 20 g·g–1, and also survive autoclaving conditions without failing. The key advantage over standard agar substrates is that they can be reused several times and also without prior sterilization. These results suggest that PE-PHs with exceptional absorption/retention properties and robustness have great potential as soilless substrates for in vitro plant cultivation.
Keywords: absorption, catalyst supports, germination, plants, porosity
Published in DKUM: 15.07.2024; Views: 114; Downloads: 10
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2. Behaviour of the subway tunnel in Algiers : physical model experimental studyAbdelbaki Seriani, Kismoune Thésard, Tayeb Serradj, 2007, original scientific article Abstract: Tunnel construction projects are too expensive to be approached directly without a preliminary small-scale model study and subsequent verification with a mathematical model, if needed. These studies enable to avoid unforeseen consequences which emerge at the time of the project realization. It is within this framework that we carried out our investigations. The behaviour of a subway tunnel in Algiers and the state of transition of the surrounding ground during digging are studied from an experimental point of view via a 1/20 physical model scale.
Keywords: tunnel, equivalent material, physical modelling, supports, deformations, rupture, loosened zone
Published in DKUM: 18.05.2018; Views: 869; Downloads: 48
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3. Influence of crosslinker and monomer ratio on bead size distribution, swelling and polymer network flexibility of 4-nitrophenylacrylate polymer supportsIrena Pulko, Peter Krajnc, 2005, original scientific article Abstract: Sphere shaped polymer supports with styrene and 4-nitrophenylacrylate as monomers and divinylbenzene (DVB) or ethyleneglycoldimethacrylate (EGDMA) as crosslinkers were prepared by free radical polymerization in suspension medium. Ratio of monomers as well as the crosslinking degree varied in order to test the influences on head size distribution, swelling and polymer network flexibility. The amount of crosslinker had an effect on bead size, average bead diameters being between 10 µm and 35 µm when 5% of crosslinker was applied and between 35 µm and 55 µm when 20% was used. The crosslinking degree also affected swelling in dichloromethane, water, methanol, toluene and acetonitrile, being more intense with lower concentrations of DVB or EGDMA. The flexibility of polymer networkwas investigated using reactions with 1,8-diaminooctane. High degrees of additional crosslinking was observed, namely between 58 and 95% indicating high flexibility of polymer network.
Keywords: organic chemistry, polymer supports, 4-nitrophenilacrylate, suspension polimerization, bead size distribution
Published in DKUM: 10.07.2015; Views: 2094; Downloads: 164
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4. Lipid layers on polyelectrolyte multilayer supportsMartin Fischlechner, Markus Zaulig, Stefan Meyer, Irina Estrela-Lopis, Luis Cuéllar, Joseba Irigoyen, Paula Pescador, Milan Brumen, Paul Messner, Sergio Moya, Edwin Donath, 2008, original scientific article Abstract: The mechanism of formation of supported lipid layers from phosphatidylcholine and phosphatidylserine vesicles in solution on polyelectrolyte multilayers was studied by a variety of experimental techniques. The interaction of zwitterionic and acidic lipid vesicles, as well as their mixtures, with polyelectrolyte supports was followed in real time by micro-gravimetry. The fabricated lipid-polyelectrolyte composite structures on top of multilayer coated colloidal particles were characterized by flow cytometry and imaging techniques. Lipid diffusion over the macroscopic scale was quantified by fluorescence recovery after photobleaching, and the diffusion was related to layer connectivity. The phospholipid-polyelectrolyte binding mechanism was investigated by infrared spectroscopy. A strong interaction of polyelectrolyte primary amino groups with phosphate and carboxyl groups of the phospholipids, leading to dehydration, was observed. Long-range electrostatic attraction was proven to be essential for vesicle spreading and rupture. Fusion of lipid patches into a homogeneous bilayer required lateral mobility of the lipids on the polyelectrolyte support. The binding of amino groups to the phosphate group of the zwitterionic lipids was too weak to induce vesicle spreading, but sufficient for strong adsorption. Only the mixture of phosphatidylcholine and phosphatidylserine resulted in the spontaneous formation of bilayers on polyelectrolyte multilayers. The adsorption of phospholipids onto multilayers displaying quarternary ammonium polymers produced a novel 3D lipid polyelectrolyte structure on colloidal particles.
Keywords: biophysics, lipids, lipid layers, electrolytes, multilayer supports
Published in DKUM: 07.06.2012; Views: 1862; Downloads: 75
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5. Preparation and characterization of poly(high internal phase emulsion) methacrylate monoliths and their application as separation mediaPeter Krajnc, Nermina Leber, Dejan Štefanec, Sandra Kontrec, Aleš Podgornik, 2005, original scientific article Abstract: Poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) monolithic supports were prepared by radical polymerisation of the continuous phase of water in oil high internal phase emulsions. Morphology of monolithic materialswas studied by scanning electron microscopy and mercury intrusion porosimetry. The ratio of phase volume and the degree of crosslinking influenced the void size and pore size distribution of resulting polymers. Void sizes between 1 and 10 m were observed and average pore sizes around 100nm. Polymers with 60, 75, 80 and 90% pore volume were prepared and even samples with highest pore volume showed good mechanical stability. They were modified to bear weak-anion exchange groups and tested on the separation of standard protein mixture containing myoglobin, conalbumine and trypsin inhibitor. Good separation was obtained in a very short time similar to the separation obtained by commercial methacrylate monoliths. However, higher dispersion was observed. Bovine serum albumin dynamic binding capacity for monolith with 90% porosity was close to 9 mg/ml.
Keywords: organic chemistry, methacrylate monoliths, preparation, emulsion polymerization, high porosity, high mechanical stability, polymer chromatographic supports, monolithic methacrylate supports, protein separation
Published in DKUM: 01.06.2012; Views: 2570; Downloads: 64
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6. Aryl acrylate based high-internal-phase emulsions as precursors for reactive monolithic polymer supportsPeter Krajnc, Dejan Štefanec, Jane F. Brown, Neil R. Cameron, 2005, original scientific article Abstract: 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.
Keywords: organic chemistry, macroporous polymers, monolithic polymer supports, emulsion polymerisation, foams, functionalization of polymers, high-internal-phase emulsions
Published in DKUM: 01.06.2012; Views: 2329; Downloads: 97
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7. Oil-in-water high internal phase emulsions for porous monolithic polymersPeter Krajnc, Dejan Štefanec, 2005, published scientific conference contribution abstract Abstract: Porous monolithic polymers are objects of many studies recently due to their wide applicability. Especially in separation methods use of monoliths is growing. Usually, porous monoliths are prepared by bulk polymerisation with the use of porogenic solvents. An alternative way of preparation is to polymerise the continuous phase of an emulsion. When the volume fraction of the internal phase exceeds 74%, the emulsion is called a HIPE (high internal phase emulsion), and a polymer derived from it, a PolyHIPE. PolyHIPEs of styrene, vinylbenzyl chloride and acrylate chemistry have been prepared from awater in oil emulsion system, where monomers are dissolved in the organic phase. We describe the reversed procedure, an oil in water high internal phaseemulsion, where monomers are water soluble. Porous polymers based on acrylic acid and crosslinked with methylenebisacrylamide were prepared by using a high internal phase emulsion with toluene as the oil phase. The influence of initiator and surfactant on the morphology was studied.
Keywords: organic chemistry, porous monolith polymers, polymer supports, preparation, emulsion polymerization, HIPE
Published in DKUM: 01.06.2012; Views: 3498; Downloads: 91
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8. 4-vinylbenzyl chloride based porous spherical polymer supports derived from water-in-oil-in-water emulsionDejan Štefanec, Peter Krajnc, 2005, original scientific article Abstract: 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.
Keywords: multiple emulsions, polymer supports, 4-vinylbenzyl chloride, solid phase synthesis, solid phase synthesis, high internal phase emulsions
Published in DKUM: 01.06.2012; Views: 2162; Downloads: 46
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9. Acrylic acid "reversed" polyHIPEsPeter Krajnc, Dejan Štefanec, Irena Pulko, 2005, original scientific article Abstract: An oil-in-water high internal phase emulsion consisting of acrylic acid, water, and a crosslinker (N,N-methylene bisacrylamide) as the water phase, and toluene as the oil phase was successfully stabilised to sustain thermal initiation of radical polymerisation resulting in porous open-cellular monolithic material. The type of initiator used influenced the average pore size ranging from approx. 708 nm to approx. 1 087 nm, as determined by mercury porosimetry.
Keywords: hydrophilic polymers, macroporous polymers, poly (acrylic acid), polyHIPE, supports
Published in DKUM: 01.06.2012; Views: 2588; Downloads: 102
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10. PolyHIPE supports in batch and flow-through Suzuki cross-coupling reactionsJane F. Brown, Peter Krajnc, Neil R. Cameron, 2005, original scientific article Abstract: As part of ongoing research efforts to discover alternative support materials to polymer beads for use in polymer-supported synthesis, particularly under flow-through conditions, this work involves the synthesis of PolyHIPE (High Internal Phase Emulsion) polymer monoliths. PolyHIPEs containing high loadings of chloromethyl groups were efficiently prepared by the direct copolymerization of 4-vinylbenzyl chloride and divinylbenzene monomers. The 'Merrifield' PolyHIPE proved to be an excellent support for batch and flow-through Suzuki cross-coupling reactions. A remarkably high yield of pure biaryl product was obtained using the PolyHIPE support in cubic form and utilizing an electron-rich boronic acid. In comparison to polymer beads, this material was found to be a much more efficient support in both batch and continuous flow modes. PolyHIPE converted a greater amount of chloromethyl groups into biaryl product under identical reaction conditions. It is suggested that the absence of channelling with PolyHIPE monoliths gives better performance under flow-through conditions than permanently porous beads.
Keywords: polymer supports, polymer monoliths, emulsion polymerisation, solid-phase synthesis, cross-coupling reactions
Published in DKUM: 01.06.2012; Views: 2404; Downloads: 103
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