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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. Poly(styrene-co-divinylbenzene-co-2-ethylhexyl)acrilate membranes with interconnected macroporous structureUrška Sevšek, Silvo Seifried, Črtomir Stropnik, Irena Pulko, Peter Krajnc, 2011, original scientific article Abstract: 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.
Keywords: membrane, porous polymers, polyHIPE, emulsions
Published in DKUM: 10.07.2015; Views: 2524; Downloads: 173
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6. 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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8. Atrazine removal by covalent bonding to piperazine functionalized PolyHIPEsIrena Pulko, Mitja Kolar, Peter Krajnc, 2007, original scientific article Abstract: The removal of atrazine from water by a solid phase extraction technique usinginsoluble polymers is described. Porous crosslinked polymers bearing piperazine moieties were prepared in a one step reaction from the precursor 4-nitrophenylacrylate incorporating polymers (PolyHIPE type prepared by the polymerization of the continuous phase of a high internal phase emulsion and polymer beads prepared by suspension polymerization). Polymers were applied tosequester atrazine from aqueous solutions with a concentration of 33 ppb andirreversible covalent bonding to the polymers was achieved. GC/MS/MS was used to monitor the dynamics of atrazine uptake and it was found that almost complete removal of atrazine was acomplished with an excess of polymer after 48 hours at room temperature. For comparison, polymer beads of identical chemistry but lower porosity were also used and showed significantly slower action (near complete removal after 72 hours).
Keywords: polymer supports, polymer scavengers, monoliths, emulsion polymerisation, solid-phase synthesis
Published in DKUM: 31.05.2012; Views: 2624; Downloads: 104
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9. POROZNI POLIAKRILATI IN POLI(VINILBENZIL KLORID) ZA IMOBILIZACIJO ORGANSKIH MOLEKULIrena Pulko, 2009, dissertation Abstract: V okviru doktorske disertacije smo proučili vpliv pogojev na pripravo akrilatnih ter vinibenzil kloridnih tipov poroznih netopnih polimernih nosilcev. Proučili smo vpliv polimerizacijskih pogojev na supramolekularno strukturo in morfologijo ter reaktivnost polimernih nosilcev. Nove polimerne nosilce v monolitni, zrnati in membranski obliki smo uporabili pri procesih separacij in čiščenja ter pri procesih katalize.
Aktiven polimerni nosilec, primeren za nadaljnje vezave in funkcionalizacije lahko pripravimo iz različnih monomerov, ki pa so pogosto dragi ali komercialno nedostopni. Zato smo v začetnem delu doktorata pripravili nosilce poli(akrilne kisline) in jih pretvorili v poli(akriloil klorid). Zaradi dobro izstopajoče kloridne skupine je možna enostavna funkcionalizacija. Proučili smo vpliv polimerizacijskih pogojev, stopnje zamreženja, dodatka porogena in komonomera ter vrste in količine stabilizatorja na omenjeno pretvorbo. Za uspešno aplikacijo je pomembna združljivost matrike in topila; običajno je matrika združljiva zgolj s polarnimi ali nepolarnimi topili. Zato smo se odločili, da v naslednji stopnji pripravimo matriko, ki bo združljiva s širokim spektrom topil. V ta namen smo pripravili zrnate in poliHIPE nosilce na osnovi vinilbenzil klorida in jih hiperzamrežili s Friedel-Craftsovo reakcijo. Med hiperzamreženjem se tvori fino porozna struktura, ki se obdrži tudi po odstranitvi topila. Polimer ima visoko specifično površino in je združljiv tako s termodinamsko ugodnimi kot neugodnimi topili. 4-metilaminopiridin smo kovalentno vezali na izhodne in hiperzamrežene nosilce ter spremljali katalitsko aktivnost imobiliziranega katalizatorja pri reakciji aciliranja in Baylis-Hillmanovi reakciji. Učinkovitost katalizatorja je močno odvisna od matrike, na katero je imobiliziran; hiperzamrežena matrika se je domala v vseh primerih izkazala kot učinkovitejša. Združljivost matrike in termodinamsko ugodnega ter neugodnega topila smo študirali z izvedbo reakcije v toluenu in dietiletru. Smotrnost imobilizacije katalizatorja smo potrdili z večkratno zaporedno uporabo imobiliziranega katalizatorja, brez bistvenega zmanjšanja učinkovitosti. Pri olefinsko metateznih reakcijah se pogosto uporabljajo katalizatorji tipa Grubbs, ki jih je potrebno po reakciji ločiti iz produktne mešanice. Zato smo pripravili nosilce na osnovi 4-nitrofenil akrilata, jih hidrolizirali, pretvorili v kislinski klorid in funkcionalizirali z 1,4-butandiolviniletrom, ter študirali vpliv morfologije in kemijske strukture nosilca na učinkovitost kovalentne vezave rutenijevega katalizatorja iz produktne mešanice. Nadalje smo študirali vpliv morfologije in kemijske strukture na odstanitev atrazina iz raztopine z nosilcem, funkcionaliziranim s piperazinom. Za odstranitev smo uporabili nosilca na osnovi 4-nitrofenil akrilata in 4-vinilbenzil klorida; slednjega smo pred funkcionalizacijo hiperzamrežili. Najučinkovitejši je bil hiperzamrežen nosilec, ki je atrazin odstranil v petnajstih minutah. Glede na to, da je aktivnost kazal tudi hiperzamrežen nefunkcionaliziran nosilec, predvidevamo da odstranitev ni posledica zgolj kovalentne vezave, ampak tudi adsorpcije.
Z namenom uporabe membran v separacijske namene v obliki membranskih modulov smo pripravili zamrežene poliHIPE membrane na osnovi glicidil metakrilata. Študirali smo vpliv dodatka etilheksil akrilata, stopnje zamreženja in dodatka interne faze na njihovo morfologijo, pretočnost in mehanske lastnosti. Vezana kapaciteta proteina bovin serum albumin je znašala 45 mg/mL, kar je več kot v primerih analognih monolitnih nosilcev.
Keywords: polimeri, makroporozni polimeri, poliHIPE, emulzija, organski katalizatorji, monoliti, membrane, poliakrilati, poli(vinilbenzil klorid)
Published in DKUM: 07.05.2009; Views: 5909; Downloads: 541
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10. Vpliv zamreženja in polimerizacijskih pogojev na fizikalno-kemijske lastnosti akrilatnih polimernih nosilcev : diplomsko deloIrena Pulko, 2004, undergraduate thesis Keywords: organska kemija, sinteze, poliakrilat, poli(akrilna kislina), poli(akriloil klorid), suspenzijska polimerizacija, zmreženi polimeri, sinteza na trdni fazi, akrilatni polimerni nosilci
Published in DKUM: 26.07.2007; Views: 4941; Downloads: 0 |
