Anthraquinone Siloxanes as Thickening Agents for Supercritical CO2

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• 作者：Michael J. O’Brien ; Robert J. Perry ; Mark D. Doherty ; Jason J. Lee ; Aman Dhuwe ; Eric J. Beckman ; Robert M. Enick
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：July 21, 2016
• 年：2016
• 卷：30
• 期：7
• 页码：5990-5998
• 全文大小：584K
• 年卷期：0
• ISSN：1520-5029

文摘

A series of aromatic amide-functionalized, low-molecular-weight polydimethylsiloxanes were synthesized, and their solubility and thickening ability in supercritical carbon dioxide (scCO₂) were evaluated. Amide-terminated polydimethylsiloxane (PDMS) oligomers with simple or electron-rich aromatic groups were found to be moderate viscosity oils, indicating that the end groups do not interact strongly enough to be thickeners. Attachment of electron-deficient aromatic groups, such as 4-nitrophenyl, biphenyl, or anthraquinone, onto these amides produced solid polysiloxanes, even at relatively higher degrees of polymerization on the PDMS core (x = 40–50). PDMS derivatives with anthraquinone-2-carboxamide (AQCA) end groups were clear, somewhat rubbery solids. These compounds were found to act as thickeners and gelators of hexanes. In addition, they were able to thicken and/or gel mixtures of hexane and scCO₂. The best results were obtained with an AQCA-terminated branched PDMS. Branched fluorenone-2-carboxamide was found to be a waxy solid that was very soluble and, therefore, not a thickener for hexane, and fluorenone-4-carboxamide was a viscous oil, indicating that these amide groups did not interact sufficiently to be useful. 10,10-Dioxothioxanthone-2-carboxamides were more efficient gelators of hexane than anthraquinone-2-carboxamides. However, they were not sufficiently soluble in scCO₂, even in the presence of hexane co-solvent, to be useful as thickeners.