Effects of functional groups on the solubilities of polyhedraloligomeric silsesquioxanes (poss) in supercritical carbon dioxide

Download
2015
Kanya, Başak
In this study, the phase behavior of the binary systems containing CO2 and various hybrid polyhedral oligomeric silsesquioxanes (POSS) with different functional groups were investigated. A high-pressure view cell was used to measure the dew-points or cloud-points at temperatures between 308K and 323K, up to 30 MPa. Among the studied POSS structures, methacryl, isooctyl and octaisobutyl POSS were observed to form homogenous solutions with CO2, while octamethyl POSS was found to be insoluble in the supercritical fluid. The solubilities of both methacryl and isooctyl POSS in supercritical carbon dioxide (scCO2) decrease with increasing temperature, while isooctyl POSS exhibits nearly an order of magnitude higher solubility than methacryl POSS at both temperatures. The octaisobutyl POSS-CO2 binary system exhibits a crossover pressure, below which the solubility of the component decreases with increasing temperature. Above this pressure, as the temperature is increased, the solubility of POSS in scCO2 increases. These results show that the functional groups of POSS affect its solubility in scCO2 and the phase behavior of the POSS-CO2 binary system significantly. After the solubility experiments the obtained phase behavior data of methacryl POSS, isooctyl POSS, and octaisobutyl POSS were correlated using density based models. The models used are; Mendez-Santiago and Teja (MST) model, Chrastil model, Bartle model, del Valle and Aguilera (del Valle) model, and Kumar and Johnston (K-J) model. All of these models gave good fit to the solubility data. In the last part of this study the obtained phase equilibrium data of POSS-CO2 binary system was used to design an environmentally benign material processing application using scCO2. In this application scCO2-soluble solid POSS, which were trifluoropropyl POSS and octaisobutyl POSS, were impregnated into a CO2-philic, biodegradable and biocompatible polymer, poly (lactic acid) (PLA) with scCO2. The morphological analysis by scanning electron microscopy (SEM) analysis and thermal characterization of the impregnated PLA films and neat PLA film by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) instruments were performed. The effect of POSS addition on glass transition temperature, melting temperature, and thermal stability were investigated. It was observed that POSS could be loaded into PLA with the supercritical fluid impregnation technique. The resulted polymer composites had an increase in their Tg with respect to neat PLA showing that the intermolecular interactions within the polymer matrix were enhanced. However, sufficient loading could not be obtained with current process conditions and POSS types loaded to obtain significant improvement in the thermal stability of the films.

Suggestions

Effects of functional groups on the solubilities of polyhedral oligomeric silsesquioxanes (POSS) in supercritical carbon dioxide
Kanya, Basak; Dilek Hacıhabiboğlu, Çerağ (2015-07-01)
The phase behavior of the binary systems containing CO2 and various hybrid polyhedral oligomeric silsesquioxanes (PUSS) with different functional groups were investigated. A high-pressure view cell was used to measure the dew-points or cloud-points at temperatures between 308 and 323 K, up to 30 MPa. Among the studied PUSS structures, methacryl, isooctyl and octaisobutyl PUSS were observed to form homogenous solutions with CO2, while octamethyl PUSS was found to be insoluble in the supercritical fluid. The ...
Effects of oxidative functionalized and aminosilanized carbon nanotubes on the crystallization behaviour of polyamide-6 nanocomposites
Kaynak, Cevdet (2014-04-01)
The purpose of this study is to investigate effects of oxidative functionalized and aminosilanized carbon nanotubes on the (1) isothermal and (2) non-isothermal crystallization kinetics of polyamide-6 by DSC analyses, and (3) crystal structure of injection molded specimens by XRD analyses. Nanocomposites were compounded by using melt mixing technique via twin screw extrusion. Due to basically very effective heterogeneous nucleation effect, both increasing amount and surface functionalization of carbon nanot...
Effect of gamma irradiation on structure and electrical properties of (Bi,Pb)(2)Sr2Ca2Cu3O10 superconductor
Albiss, BA; Ozkan, H; Bocuk, H; Hasanlı, Nızamı; Ercan, I (1997-01-01)
Specimens of pure and Pb-doped high-T-c superconductors Bi2Sr2Ca2Cu3O10 (BSCCO) were irradiated with gamma-rays up to an integrated dose of about 225 MR. The variations of normal state resistance, transition temperature, critical current and lattice parameters with gamma-irradiation were studied. The normal state resistance increases with increase of gamma-dose at zero applied magnetic field, whereas the transition temperature and the critical current decrease with the same gamma-dose. The intensities of th...
EFFECT OF π-BRIDGES ON ELECTROCHEMICAL AND PHOTOVOLTAIC PROPERTIES OF BENZOTHIADIAZOLE AND BENZODITHIOPHENE BASED CONJUGATED POLYMERS
Dikbıyık, Dilan Ece; Çırpan, Ali; Hızalan Özsoy, Gönül; Department of Chemistry (2022-1-28)
In this study, a series of the Donor -π bridge- Acceptor type conjugated polymers (PT1, PT2, and PT3) were designed and synthesized via Pd-catalyzed Stille polycondensation reactions. Synthesized polymers were used as donor moieties and blended with acceptor unit PC71BM to form the active layer of the bulk heterojunction organic solar cell (BHJ OSC). Polymers contain electron-deficient benzothiadiazole (BT) as acceptor unit and electron-rich benzodithiophene (BDT) as donor unit. Moreover, thiophene [T], sel...
Effect of hydrogen ion-exchange capacity on activity of resin catalysts in tert-amyl-ethyl-ether synthesis
Boz, N; Doğu, Timur; Murtezaoglu, K; Dogu, G (Elsevier BV, 2004-08-10)
Activities of ion-exchange resin catalysts, having different hydrogen exchange capacities ranging between 5.1 and 1.3 meq H+/g, on the etherification reactions of 2M1B (2-methyl-1-butene) and 2M2B (2-methyl-2-butene) with ethanol were experimentally tested in a fixed bed reactor. These catalysts were prepared by the heat treatment of Amberlyst-15 catalysts at 220 degreesC at different durations of time and also by the synthesis of sulfonated styrene divinyl benzene cross-linked resins. Activity of these cat...
Citation Formats
B. Kanya, “Effects of functional groups on the solubilities of polyhedraloligomeric silsesquioxanes (poss) in supercritical carbon dioxide,” M.S. - Master of Science, Middle East Technical University, 2015.