Atomistic and Mesoscopic Simulations of the Structure of CO2 with Fluorinated and Nonfluorinated Copolymers
AG Goicochea and A Firoozabadi, JOURNAL OF PHYSICAL CHEMISTRY C, 123, 17010-17018 (2019).
Viscosification of CO2 by a low concentration of functional molecules is a prized task. It has two important applications. One is in fracturing of shale formation and the other is sweep efficiency improvement on the subsurface in hydrocarbon production. Toward that goal, we investigate the molecular structure of copolymers in CO2 based on simulations at the atomistic and mesoscopic scales at various copolymer concentrations, pressure, and temperature. The effect of a small amount of water on the structure is also investigated., Three types of polymers are examined: fluorinated acrylate polymerized with styrene and two non-fluorinated copolymers. All of them, from experimental reports, show their effectiveness in increasing the viscosity of CO2 by varying degrees. Our results show that there emerge three basic structures: dispersion in CO2 formation of micelle-like aggregates, and interconnection of aggregates. In one of the three functional molecules, a small amount of water decreases the effective length and promotes the formation of aggregates. It is found that branched structures are favorable for solubility in CO2 and that aggregation is promoted by intermolecular it stacking. We expect this work to set the stage for molecular engineering in effective CO2 viscosification.
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