Enhanced solubility of siloxy-modified polyhedral oligomeric silsesquioxanes in supercritical carbon dioxide

Alkyl siloxy functionalization increases the solubility of polyhedral oligomeric silsesquioxanes (POSS) in supercritical carbon dioxide over an order of magnitude compared to its counterpart with fluoroalkyl groups. The studied component, octatrimethylsiloxy POSS also exhibits higher solubility than other previously studied POSS types with various alkyl and methacryl groups. The octatrimethylsiloxy POSS-CO2 solid-vapor equilibrium curves have been constructed at temperatures between 308 and 328 K by measuring cloud points. The highest measured solubility of octatrimethylsiloxy POSS was 0.176 wt. fr., corresponding to 0.0083 mol fr., at 13.36 MPa, 328 K, and CO2 density of 0.59 g/cm(3). The solubility versus CO2 density isotherms fall on a master curve up to about 2 x 10(-3) mol fraction, while at higher concentrations, higher solubility was attained with increasing temperature. The experimental data were correlated using various semi-empirical density-based models which provided satisfactory correlations.


Phase Behavior of Carbon Dioxide and Polyhedral Oligomeric Silsesquioxanes with Two Different Functional Groups
Dumanlilar, Beril; Dilek Hacıhabiboğlu, Çerağ (Elsevier BV, 2020-09-01)
Phase behavior of carbon dioxide and polyhedral oligomeric silsesquioxanes (POSS) modified with two different functional groups is studied in the temperature range of 308-323 K, up to 22 MPa. Different than the common types, one of the eight functional groups attached to the Si atoms of these POSS is a CO2-philic functional group, methacryl, while the rest are branched alkyl chains, either isooctyl (MIOPOSS) or isobutyl (MIBPOSS). Methacrylisobutyl POSS-CO2 binary system exhibits pressure-induced melting te...
Phase behavior of 1,3,5-tri-tert-butylbenzene-carbon dioxide binary system
Dilek Hacıhabiboğlu, Çerağ; Gulari, Esin (Elsevier BV, 2008-01-01)
1,3,5-tri-tert-butylbenzene (TTBB) is solid at ambient conditions, and has substantial solubility in liquid and supercritical carbon dioxide. We present the phase behavior of TTBB-CO2 binary system at temperatures between 298 and 328 K and at pressures up to 20 MPa. Phase diagrams showing the liquid-vapor, solid-liquid and solid-vapor equilibrium envelopes are constructed by pressure-volume-temperature measurements in a variable-volume sapphire cell. TTBB is highly soluble in CO2 over a wide range of compos...
AM1 treatment of phenylboronic acid esters of glycerol
Türker, Burhan Lemi (Elsevier BV, 2004-05-14)
Phenylboronic acid esters of glycerol, which involve 1,2- and 1,3-sites of glycerol for esterification followed by complex formation with the remaining -OH group of glycerol have been considered for AM1(RHF) type semiempirical quantum chemical calculations, in vacuum as well as in aqueous medium. All the species were found to be stable and exothermic. The stability order among the various species considered was established. 1,2-type ester in vacuum or aqueous medium was found to be more stable than the resp...
High-temperature bromination XIII: Bromination of dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate
Simsek, N; Arici, C; McKee, ML; Ulku, D; Balcı, Metin (Springer Science and Business Media LLC, 2001-08-01)
The electrophilic addition of bromine to dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate 10 at 0 and -60 degreesC led in high yield to the formation of dibromide 11. However, high-temperature bromination of 10 in carbon tetrachloride at 77 degreesC gave four products 12-15, three of them with nonrearranged skeleton. Similarly, bromination of the dibromides 14 and 15 at 77 degreesC yielded the nonrearranged tetrabromides 13 and 16, respectively. The structure of the tetrabromide 13 was solved b...
Optimization of supercritical carbon dioxide extraction of antioxidants from roasted wheat germ based on yield, total phenolic and tocopherol contents, and antioxidant activities of the extracts
Gelmez, Niluefer; Kincal, N. Suzan; Yener, Meryem Esra (Elsevier BV, 2009-04-01)
Effects of pressure (148-602 bar), temperature (40-60 degrees C) and time (10-60 min) on antioxidant (phenolics and tocopherols) contents and antioxiclant activities of supercritical carbon dioxide (SC-CO2) extracts of roasted wheat germ were determined, using central composite rotatable design. The dependent variables were yield (%), total phenolic contents (TPC, mg gallic acid equivalent (GAE)/g extract), total tocopherol contents (TTC, mg tocopherol/g extract) and antioxidant activities (AA, mg scavenged...
Citation Formats
C. Demirtas and Ç. Dilek Hacıhabiboğlu, “Enhanced solubility of siloxy-modified polyhedral oligomeric silsesquioxanes in supercritical carbon dioxide,” JOURNAL OF SUPERCRITICAL FLUIDS, pp. 358–364, 2019, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/36172.