| | SLO | ENG | Cookies and privacy

Bigger font | Smaller font

Search the digital library catalog Help

Query: search in
search in
search in
search in
* old and bologna study programme

Options:
  Reset


1 - 8 / 8
First pagePrevious page1Next pageLast page
1.
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, original scientific article

Abstract: 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.
Keywords: organic chemistry, polymerization, monolithic polymers, HIPE, emulsions, porous materials, methacrylates
Published: 31.05.2012; Views: 1357; Downloads: 45
URL Link to full text

2.
Oil-in-water high internal phase emulsions for porous monolithic polymers
Peter 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: 01.06.2012; Views: 2162; Downloads: 58
URL Link to full text

3.
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, 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: 01.06.2012; Views: 1205; Downloads: 61
URL Link to full text

4.
Preparation and characterization of poly(high internal phase emulsion) methacrylate monoliths and their application as separation media
Peter 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: 01.06.2012; Views: 1343; Downloads: 25
URL Link to full text

5.
Influence of crosslinker and monomer ratio on bead size distribution, swelling and polymer network flexibility of 4-nitrophenylacrylate polymer supports
Irena 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: 10.07.2015; Views: 861; Downloads: 74
.pdf Full text (510,34 KB)
This document has many files! More...

6.
The influence of thermoplastic elastomers on morphological and mechanical properties of PP/talc composites
Matjaž Denac, Vojko Musil, 1999, original scientific article

Abstract: Recent investigations have shown that modification of polymer matrix with filler and elastomers significantly affects composite's mechanical properties. Isotactic PP modified with either untreated or treated talc and either SEBS or SEBS-gMA were used in these investigations. Samples were prepared by melt-mixing in a Brabender kneading chamber and were compression molded into plates on a laboratory press. The composites were characterised by measuring mechanical properties (Young's modulus, yield stress, notched impact strength) and by defining morphology. Binary sistems PP/talc and PP/elastomer containing up to 16 vol.% of talc and up to 10 vol.% of elastomer, as well as ternary PP/talc/elastomer composites with 12 vol.% talc were investigated. Ternary composite's yield stress was also calculated by semiempirical equations. We have found out, that the use of treated modifiers (talc or elastomer) improves adhesion with matrix, which reflects on mechanical properties as better stress transfer.
Keywords: organic chemistry, polymers, thermoplastics, composites, characterization, chemistry, plastics, elastomers, morphology, mechanical properties
Published: 10.07.2015; Views: 877; Downloads: 35
.pdf Full text (367,27 KB)
This document has many files! More...

7.
The crystal and molecular structures of two reaction products of geminal dicyano oxirane with thiohydantoine (compound I) and thioxobenzoxazole (compound II)
Ivan Leban, Alenka Majcen Le Marechal, Albert Robert, 1993, original scientific article

Abstract: The crystal and molecular structures of two reaction products of geminal dicyano oxiranes with thiohydantoione and thioxobenzoxazole have been determinated from ▫$Mo-K_\alpha$▫ X-ray diffraction data. The two reaction products were: 2H-2-(p-tolyl)-imidazol[1,2-b]thiazole-3,6-dione (compound I) and Z-3-benzoxazole-3-phenyl-2-oxo-2-propanenitrile (compound II) with the following crystal data at 293(1) K: Compound I, ▫$C_{12}H_{10}N_2O_2S$▫, monoclinic ▫$P2_1/c$▫, a=15057(3), b=5.200(3), c=14.724(4) Å, ▫$\beta=104.24(3)°$▫, Z=4; final R and ▫$R_w$▫ values were 0.034 and 0.049 for1647 observed reflexions. Compound II, ▫$C_{16}H{10}N_2O_2$▫, monoclinic, ▫$P2_1/n$▫, a=14.396(3), b=4.326(1), c=21.335(4) Å, ▫$\beta-107.79(1)°$▫, Z=4;final R and ▫$R_w$▫ values 0.040 and 0.053 for 1516 observed reflections.
Keywords: organic chemistry, crystal structure, chemical reactions, oxiranes, coordination compounds, structural chemistry
Published: 05.07.2017; Views: 416; Downloads: 38
.pdf Full text (16,17 MB)
This document has many files! More...

8.
A novel approach to N,N'-dimethyl and N,N'-ethylene bridged dibenzodithiadiazafulvalane
Zdenko Časar, Dominique Lorcy, Ivan Leban, Alenka Majcen Le Marechal, 2002, original scientific article

Abstract: A novel approach to electron rich olefins, such as dibenzodithiadiazafulvalenes (DTDAFs) is reported. These compounds have been prepared by alkalination of the benzothiazole-2-thione ring. The first crystal structure of the N,N'-dimethyl dibenzoDTDAF dicationis also reported.
Keywords: organic chemistry, benzothiazole, thermal rearrangement, dithiadiazafulvalene, dication
Published: 17.08.2017; Views: 238; Downloads: 57
.pdf Full text (365,86 KB)
This document has many files! More...

Search done in 0.12 sec.
Back to top
Logos of partners University of Maribor University of Ljubljana University of Primorska University of Nova Gorica