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Yang XD, Chen W, Ren Y, Chu LY. Exploration of the Adsorption Kinetics of Surfactants at the Water-Oil Interface via Grand-Canonical Molecular Dynamics Simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:1277-1286. [PMID: 35015552 DOI: 10.1021/acs.langmuir.1c03205] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
It is well-known that surfactants tend to aggregate into clusters or micelles in aqueous solutions due to their special structures, and it is difficult for the surfactant molecules involved in the aggregation to move spontaneously to the oil-water interface. In this article, we developed a new grand-canonical molecular dynamics (GCMD) model to predict the saturated adsorption amount of surfactant with constant concentration of surfactant molecules in the bulk phase, which can prevent surfactants aggregating in the bulk phase and get the atomic details of the interfacial structural change with increase of the adsorption amount through a single GCMD run. The adsorption of anionic surfactant sodium dodecyl sulfate (SDS) at the heptane-water interface was studied to validate the model. The saturated adsorption amount obtained from the GCMD simulation is consistent with the experimental results. The adsorption kinetics of SDS molecules during the simulation can be divided into three stages: linear adsorption stage, transition adsorption stage, and dynamic equilibrium stage. We also carried out equilibrium molecular dynamics (EMD) simulations to compare with GCMD simulation. This GCMD model can effectively reduce the simulation time with correct prediction of the interfacial saturation adsorption. We believe the GCMD method could be especially helpful for the computational study of surfactant adsorption under complex environments or emulsion systems with the adsorption of multiple types of surfactants.
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Affiliation(s)
- Xue-Dan Yang
- School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
- State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan 610065, China
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
| | - Wei Chen
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049,China
- Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Ying Ren
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049,China
- Innovation Academy for Green Manufacture, Chinese Academy of Sciences, Beijing 100190, China
| | - Liang-Yin Chu
- School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
- State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, Sichuan 610065, China
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Affiliation(s)
- Michael P. Allen
- Department of Physics, University of Warwick, Coventry, UK
- H. H. Wills Physics Laboratory, Royal Fort, Bristol, UK
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Jana PK, Chen W, Alava MJ, Laurson L. Nanoscale liquid crystal lubrication controlled by surface structure and film composition. Phys Chem Chem Phys 2018; 20:18737-18743. [PMID: 29961781 DOI: 10.1039/c8cp03353f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Liquid crystals have emerged as potential candidates for next-generation lubricants due to their tendency to exhibit long-range ordering. Here, we construct a full atomistic model of 4-cyano-4-hexylbiphenyl (6CB) nematic liquid crystal lubricants mixed with hexane and confined by mica surfaces. We explore the effect of the surface structure of mica, as well as lubricant composition and thickness, on the nanoscale friction in the system. Our results demonstrate the key role of the structure of the mica surfaces, specifically the positions of potassium (K+) ions, in determining the nature of sliding friction with monolayer lubricants, including the presence or absence of stick-slip dynamics. With the commensurate setup of confining surfaces, when the grooves created between the periodic K+ ions are parallel to the sliding direction we observe a lower friction force as compared to the perpendicular situation. Random positions of ions exhibit even smaller friction forces with respect to the previous two cases. For thicker lubrication layers the surface structure becomes less important and we observe a good agreement with the experimental data on bulk viscosity of 6CB and the additive hexane. In case of thicker lubrication layers, friction may still be controlled by tuning the relative concentrations of 6CB and hexane in the mixture.
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Affiliation(s)
- Pritam Kumar Jana
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto, Espoo, Finland.
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Mendonça ACF, Goujon F, Malfreyt P, Tildesley DJ. Monte Carlo simulations of the static friction between two grafted polymer brushes. Phys Chem Chem Phys 2016; 18:6164-74. [DOI: 10.1039/c5cp07374j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A configurational bias Monte Carlo method has been developed to calculate the static friction between two grafted polymer brushes.
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Affiliation(s)
| | - Florent Goujon
- Clermont Université
- Université Blaise Pascal
- Institut de Chimie de Clermont-Ferrand
- UMR CNRS 6296
- F-63000 Clermont-Ferrand
| | - Patrice Malfreyt
- Clermont Université
- Université Blaise Pascal
- Institut de Chimie de Clermont-Ferrand
- UMR CNRS 6296
- F-63000 Clermont-Ferrand
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Chen W, Foster AS, Alava MJ, Laurson L. Stick-slip control in nanoscale boundary lubrication by surface wettability. PHYSICAL REVIEW LETTERS 2015; 114:095502. [PMID: 25793825 DOI: 10.1103/physrevlett.114.095502] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Indexed: 06/04/2023]
Abstract
We study the effect of atomic-scale surface-lubricant interactions on nanoscale boundary-lubricated friction by considering two example surfaces-hydrophilic mica and hydrophobic graphene-confining thin layers of water in molecular dynamics simulations. We observe stick-slip dynamics for thin water films confined by mica sheets, involving periodic breaking-reforming transitions of atomic-scale capillary water bridges formed around the potassium ions of mica. However, only smooth sliding without stick-slip events is observed for water confined by graphene, as well as for thicker water layers confined by mica. Thus, our results illustrate how atomic-scale details affect the wettability of the confining surfaces and consequently control the presence or absence of stick-slip dynamics in nanoscale friction.
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Affiliation(s)
- Wei Chen
- Department of Applied Physics, COMP Centre of Excellence, Aalto University, P.O. Box 11100, 00076 Aalto, Espoo, Finland
- Supercomputing Center of CAS, Computer Network Information Center, Chinese Academy of Sciences, Beijing 100190, China
| | - Adam S Foster
- Department of Applied Physics, COMP Centre of Excellence, Aalto University, P.O. Box 11100, 00076 Aalto, Espoo, Finland
| | - Mikko J Alava
- Department of Applied Physics, COMP Centre of Excellence, Aalto University, P.O. Box 11100, 00076 Aalto, Espoo, Finland
| | - Lasse Laurson
- Department of Applied Physics, COMP Centre of Excellence, Aalto University, P.O. Box 11100, 00076 Aalto, Espoo, Finland
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Manzato C, Foster AS, Alava MJ, Laurson L. Friction control with nematic lubricants via external fields. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:012504. [PMID: 25679635 DOI: 10.1103/physreve.91.012504] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Indexed: 06/04/2023]
Abstract
We study the connection between sliding friction and the phase behavior of a simple rigid bead-necklace model of a liquid crystal (LC) lubricant layer confined between two parallel plates. The dynamics is dependent on competing LC ordering mechanisms, including the direction of sliding, and an applied (electric) field. Together with temperature and an applied pressure, determining whether the lubricant is in a fluidlike isotropic state or in a layered in-plane nematic state, such ordering is found to control the frictional properties of the lubricant. Our extensive molecular dynamics simulations reveal in a detailed manner how friction can be controlled via applied fields. The results are expected to help in designing novel strategies to develop lubricants with dynamically controllable properties.
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Affiliation(s)
- Claudio Manzato
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, Aalto 00076, Finland
| | - Adam S Foster
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, Aalto 00076, Finland
| | - Mikko J Alava
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, Aalto 00076, Finland
| | - Lasse Laurson
- COMP Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 11100, Aalto 00076, Finland
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