title: Molecular dynamics study of di-CF4 based reverse micelles in supercritical CO2.
abstract: Reverse micelles (RMs) in supercritical CO2(scCO2) are promising alternatives for organic solvents, especially when both polar and non-polar components are involved. Fluorinated surfactants, particularly double-chain fluorocarbon surfactants, are able to form well-structured RMs in scCO2. The inherent self-assembly mechanisms of surfactants in scCO2are still subject to discussion. In this study, molecular dynamics simulations are performed to investigate the self-aggregation behavior of di-CF4 based RMs in scCO2, and stable and spherical RMs are formed. The dynamics process and the self-assembly structure in the RMs reveal a three-step mechanism to form the RMs, that is, small RMs, rod-like RMs and fusion of the rod-like RMs. Hydrogen-bonds between headgroups and water molecules, and salt bridges linking Na+ions, headgroups and water molecules enhance the interfacial packing efficiency of the surfactant. The results show that di-CF4 molecules have a high surfactant coverage at the RM interface, implying a high CO2-philicity. This mainly results from bending of the short chain (C-COO-CH2-(CF2)3-CF3) due to the flexible carboxyl group. The microscopic insight provided in this study is helpful in understanding surfactant self-assembly phenomena and designing new CO2-philic surfactants.
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, Shandong, China. liubing19720115@gmail.com and NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway. jianying.he@ntnu.no.
authors.forename: Bing
authors.initials: B
authors.lastname: Liu
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, Shandong, China. liubing19720115@gmail.com.
authors.forename: Xinpeng
authors.initials: X
authors.lastname: Tang
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, Shandong, China. liubing19720115@gmail.com.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Fang
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, Shandong, China. liubing19720115@gmail.com.
authors.forename: Xiaoqi
authors.initials: X
authors.lastname: Li
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, Shandong, China. liubing19720115@gmail.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway. jianying.he@ntnu.no.
authors.forename: Zhiliang
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, Shandong, China. liubing19720115@gmail.com.
authors.forename: Yue
authors.initials: Y
authors.lastname: Shen
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, Shandong, China. liubing19720115@gmail.com.
authors.forename: Youguo
authors.initials: Y
authors.lastname: Yan
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, Shandong, China. liubing19720115@gmail.com.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Sun
authors.affiliation: NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim, 7491, Norway. jianying.he@ntnu.no.
authors.forename: Jianying
authors.initials: J
authors.lastname: He