Atomistic and Mesoscopic Simulations of the Structure of CO₂ with Fluorinated and Nonfluorinated Copolymers

Abstract

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 π-stacking. We expect this work to set the stage for molecular engineering in effective CO2 viscosification.

Scaling Properties of Soft Matter in Equilibrium and Under Stationary Flow

“…This accuracy of DPD simulations in capturing scaling behavior in polymer brushes is not accidental as it has been found to be successful in other applications, see for example [22]. Additional examples are displayed in Fig.…”

“…The natural probability distribution function of the DPD model is found to be that of the canonical ensemble [8], where N (the total particle number), V, and T are kept constant, although it is equally possible to solve the system using the Monte Carlo algorithm [4] under various ensembles of interest [18 -20]. Polymer chains can be constructed following the Murat -Grest beadspring linear chain model [21], while surfaces can either be introduced using effective force fields [19,22] or by freezing layers of particles [23]. The chemical composition of the DPD particles is incorporated into the value chosen for the conservative interaction strength, aij, see eq.…”

Modeling of Branched Thickening Polymers under Poiseuille Flow Gives Clues as to How to Increase a Solvent’s Viscosity

“…Branched polymers were used because experiments [5,10,17] and simulations [53,61] have shown them to be more effective in raising the viscosity than linear ones, under similar thermodynamic conditions. The viscosity is obtained as a function of polymer concentration, branch length and flexibility and as a function of angular bonding strength.…”

Self – assembly of model surfactants as reverse micelles in nonpolar solvents and their role as interfacial tension modifiers

“…The need to understand the microscopic mechanisms that play a role in more complex systems at different concentrations and thermodynamic conditions using shorter simulation times, calls for accurate mesoscale techniques. It has been shown recently that a multiscale simulation based on atomistic and mesoscopic scales of polymers' role in thickening CO2 offers useful insights into their aggregation mechanisms [54]. Using this approach, the role of a small amount of water in the system configuration was also examined [54].…”

“…It has been shown recently that a multiscale simulation based on atomistic and mesoscopic scales of polymers' role in thickening CO2 offers useful insights into their aggregation mechanisms [54]. Using this approach, the role of a small amount of water in the system configuration was also examined [54].…”