Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 27Citation - Scopus: 31Fluoroacrylate-Aromatic Acrylate Copolymers for Viscosity Enhancement of Carbon Dioxide(Elsevier Ltd., 2019) Kılıç, Sevgi; Enick, Robert M.; Beckman, Eric J.The effect of the structure of aromatic acrylate-fluoroacrylate copolymers on CO2 viscosity at elevated pressures was investigated. These copolymers were all found to be miscible with CO2 at pressures between 10-15 MPa (295 K) and induce an increase in the viscosity to some degree. It appears that stacking of aromatic rings is the key factor in viscosity enhancement. The results showed that viscosity of the solution increases with the increasing content of the aromatic acrylate unit in the copolymer, but a point is reached beyond which additional comonomer causes the relative viscosity to drop, suggesting that the aromatic rings associate through intramolecular rather than intermolecular interactions beyond the optimum value. The most effective CO2 thickener identified in this study was the 29% phenyl acrylate-71% fluoroacrylate copolymer. However, the presence of a spacer (methyl or ethyl) between the backbone and the aromatic group substantially diminished the viscosity enhancement.Article Citation - WoS: 15Citation - Scopus: 13Phase Behavior of Dspc/Peg40st Mixtures at Higher Emulsifier Contents(Elsevier Ltd., 2018) Kılıç, Sevgi; Bölükçü, Elif ŞenizPhase behaviors of 1,2-Distearoyl-sn-glycero-3-phosphocholine (DSPC) and polyoxyethylene(40)stearate (PEG40St) were investigated with Langmuir monolayer isotherms and Brewster angle microscopy (BAM) imaging at DSPC/PEG40St molar ratios ranging from 9:1 to 5:5. Two plateaus were found in the Langmuir isotherms which were relatively shorter for the 9:1 mixture and extended significantly by increasing the PEG40St content, indicating that the PEG40St squeezed out whereas more emulsifier retained in the monolayer at higher PEG40St contents. A strong hysteresis was observed when the mixed monolayers were subjected to compression-expansion cycles. The degree of hysteresis for the first cycles also increased with increasing PEG40St content in the monolayer. Gray scale intensities in the Brewster angle microscopy images were determined for pure DSPC and pure PEG40St and a scale was established to better interpret the morphologies for the mixtures. Bud and vessels formed during the PEG40St squeezed out upon compression. Upon expansion, PEG40St and DSPC is reappeared on the monolayer. When considered BAM images together with the Langmuir isotherm, PEG40St molecules were found to be well distributed within the DSPC molecules at lower DSPC/PEG40St mole ratios and mostly phase separated at higher mole ratios. It was concluded that higher PEG40St content would be advantageous for the design of an efficient and cheaper ultrasound contrast agents.Article Citation - WoS: 14Citation - Scopus: 15Effect of Carbonic Anhydrase on Caco3 Crystallization in Alkaline Solution(American Chemical Society, 2016) Molva, Murat; Kılıç, Sevgi; Özdemir, EkremThe effect of bovine carbonic anhydrase (CA) on calcium carbonate (CaCO3) crystallization was investigated. A new method was developed to estimate the biocatalytic activity of CA in alkaline solution. The CA was immobilized within polyurethane (PU) foam, and compared its biocatalytic activity with the free-CA and bare-PU foam. A minireactor was created in a calcium hydroxide (Ca(OH)2) solution in order to control the CO2 transfer rate, and reproducible results were obtained. It was found that the free-CA lost its activity in less than 6 min at pH 12.5 in alkaline Ca(OH)2 solution. The CaCO3 crystallization rates for the immobilized-CA were found to be a U-shape, relatively lower at lower immobilized-CA amounts compared to those for the free-CA and bare-PU foam and higher when the amount of immobilized-CA increased. It was concluded that a higher immobilized-CA amount is required to accelerate the CaCO3 crystallization rates in Ca(OH)2 solution.Article Citation - WoS: 40Citation - Scopus: 46Influence of Tert-Amine Groups on the Solubility of Polymers in Co2(Elsevier Ltd., 2009) Kılıç, Sevgi; Wang, Yang; Johnson, J. Karl; Beckman, Eric J.; Enick, Robert M.There is a need to develop new, non-fluorous polymers that are highly soluble in CO2. Experimental evidence indicates that tertiary amine and pyridine groups may exhibit favorable Lewis acid-Lewis base type interactions with CO2. It is therefore reasonable to assume that incorporation of tertiary amines into the side chain or backbone of non-fluorous polymers may impart a degree of CO2-solubility to the polymer. We present experimental results for eight different tert-amine-containing polymers. Of these polymers, only propyl dimethylamine-functionalized poly(dimethylsiloxane) is soluble in CO2 at temperatures and pressures accessible in our experiments, but even this polymer is less soluble than non-functionalized poly(dimethylsiloxane) at the same chain length. We have performed ab initio calculations on tertiary amine-containing moieties representative of some of the polymers examined experimentally. Our calculations confirm that amine-CO2 interactions are indeed energetically favorable. However, we also find that the moiety self-interactions are typically more favorable than the CO2-moiety interactions. This indicates that the lack of solubility of amine-containing polymers in CO2 is a direct result of strong polymer-polymer interactions.