1
|
Urano R, Pantelopulos GA, Straub JE. Aerosol-OT Surfactant Forms Stable Reverse Micelles in Apolar Solvent in the Absence of Water. J Phys Chem B 2019; 123:2546-2557. [PMID: 30688469 DOI: 10.1021/acs.jpcb.8b07847] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Normal micelle aggregates of amphiphilic surfactant in aqueous solvents are formed by a process of entropically driven self-assembly. The self-assembly of reverse micelles from amphiphilic surfactant in a nonpolar solvent in the presence of water is considered to be an enthalpically driven process. Although the formation of normal and reverse surfactant micelles has been well characterized in theory and experiment, the nature of dry micelle formation, from amphiphilic surfactant in a nonpolar solvent in the absence of water, is poorly understood. In this study, a theory of dry reverse micelle formation is developed. Variation in free energy during micelle assembly is derived for the specific case of aerosol-OT surfactant in isooctane solvent using atomistic molecular dynamics simulation analyzed using the energy representation method. The existence and thermodynamic stability of dry reverse micelles of limited size are confirmed. The abrupt occurrence of monodisperse aggregates is a clear signature of a critical micelle concentration, commonly observed in the formation of normal surfactant micelles. The morphology of large dry micelles provides insight into the nature of the thermodynamic driving forces stabilizing the formation of the surfactant aggregates. Overall, this study provides detailed insight into the structure and stability of dry reverse micelles assembly in a nonpolar solvent.
Collapse
Affiliation(s)
- Ryo Urano
- Chemistry Department , Boston University , 590 Commonwealth Avenue , Boston , Massachusetts 02215 , United States
| | - George A Pantelopulos
- Chemistry Department , Boston University , 590 Commonwealth Avenue , Boston , Massachusetts 02215 , United States
| | - John E Straub
- Chemistry Department , Boston University , 590 Commonwealth Avenue , Boston , Massachusetts 02215 , United States
| |
Collapse
|
2
|
Yoshii N, Nimura Y, Fujimoto K, Okazaki S. Spherical harmonics analysis of surface density fluctuations of spherical ionic SDS and nonionic C12E8 micelles: A molecular dynamics study. J Chem Phys 2017; 147:034906. [DOI: 10.1063/1.4994698] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Noriyuki Yoshii
- Center for Computational Science, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
- Department of Applied Chemistry, Nagoya University, Nagoya 464-8603, Japan
| | - Yuki Nimura
- Department of Applied Chemistry, Nagoya University, Nagoya 464-8603, Japan
| | - Kazushi Fujimoto
- Department of Applied Chemistry, Nagoya University, Nagoya 464-8603, Japan
| | - Susumu Okazaki
- Department of Applied Chemistry, Nagoya University, Nagoya 464-8603, Japan
- Center for Computational Science, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
| |
Collapse
|
3
|
Kislenko SA, Razumov VF. Molecular dynamics study of micellization thermodynamics in AOT/hexane system. COLLOID JOURNAL 2017. [DOI: 10.1134/s1061933x17010094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
4
|
Yuan F, Larson RG. Multiscale Molecular Dynamics Simulations of Model Hydrophobically Modified Ethylene Oxide Urethane Micelles. J Phys Chem B 2015; 119:12540-51. [PMID: 26337615 DOI: 10.1021/acs.jpcb.5b04895] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The flower-like micelles of various aggregation numbers of a model hydrophobically modified ethylene oxide urethane (HEUR) molecule, C16E45C16, and their corresponding starlike micelles, containing the surfactants C16E22 and C16E23, were studied by atomistic and coarse-grained molecular dynamic (MD) simulations. We used free energies from umbrella sampling to calculate the size distribution of micelle sizes and the average time for escape of a hydrophobic group from the micelle. Using the coarse-grained MARTINI force field, the most probable size of the model HEUR molecule was thereby determined to be about 80 hydrophobes per micelle and the average hydrophobe escape time to be about 0.1 s, both of which are consistent with previous experimental studies. Atomistic simulations reveal that hydrogen bond formation and the mean lifetime of hydration waters of the poly(ethylene oxide) (or PEO) groups are location-dependent in the HEUR micelle, with PEO groups immediately adjacent to the C16 groups forming the fewest hydrogen bonds with water and having hydration waters with longer lifetimes than those of the PEO groups located further away from the C16 groups.
Collapse
Affiliation(s)
- Fang Yuan
- Department of Chemical Engineering and ‡Departments of Mechanical Engineering, Biomedical Engineering, and Macromolecular Science and Engineering Program, University of Michigan , Ann Arbor, Michigan 48109, United States
| | - Ronald G Larson
- Department of Chemical Engineering and ‡Departments of Mechanical Engineering, Biomedical Engineering, and Macromolecular Science and Engineering Program, University of Michigan , Ann Arbor, Michigan 48109, United States
| |
Collapse
|
5
|
Wang J, Guo K, An L, Müller M, Wang ZG. Micelles of Coil−Comb Block Copolymers in Selective Solvents: Competition of Length Scales. Macromolecules 2010. [DOI: 10.1021/ma901977h] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jiafang Wang
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China
- Institut für Theoretische Physik, Georg-August Universität, D-37077 Göttingen, Germany
| | - Kunkun Guo
- College of Materials Science and Engineering, Hunan University, Changsha 410082, P. R. China
| | - Lijia An
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China
| | - Marcus Müller
- Institut für Theoretische Physik, Georg-August Universität, D-37077 Göttingen, Germany
| | - Zhen-Gang Wang
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125
| |
Collapse
|
6
|
Lauw Y. Equilibrium morphologies of nonionic lipid–nanoparticle mixtures in water: A self-consistent mean-field prediction. J Colloid Interface Sci 2009; 332:491-6. [DOI: 10.1016/j.jcis.2008.12.053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 12/03/2008] [Accepted: 12/18/2008] [Indexed: 10/21/2022]
|
7
|
Longa L, Pajak G, Wydro T. Stability of biaxial nematic phase for systems with variable molecular shape anisotropy. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:011703. [PMID: 17677467 DOI: 10.1103/physreve.76.011703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Indexed: 05/16/2023]
Abstract
We study the influence of fluctuations in molecular shape on the stability of the biaxial nematic phase by generalizing the mean-field model of Mulder and Ruijgrok [Physica A 113, 145 (1982)]. We limit ourselves to the case when the molecular shape anisotropy, represented by the alignment tensor, is a random variable of an annealed type. A prototype of such behavior can be found in lyotropic systems--a mixture of potassium laurate, 1-decanol, and D2O , where distribution of the micellar shape adjusts to actual equilibrium conditions. Further examples of materials with the biaxial nematic phase, where molecular shape is subject to fluctuations, are thermotropic materials composed of flexible trimericlike or tetrapodlike molecular units. Our calculations show that the Gaussian equilibrium distribution of the variables describing molecular shape (dispersion force) anisotropy gives rise to new classes of the phase diagrams, absent in the original model. Depending on properties of the shape fluctuations, the stability of the biaxial nematic phase can be either enhanced or depressed, relative to the uniaxial nematic phases. In the former case the splitting of the Landau point into two triple points with a direct phase transition line from isotropic to biaxial phase is observed.
Collapse
Affiliation(s)
- Lech Longa
- Marian Smoluchowski Institute of Physics, Department of Statistical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University, Reymonta 4, Kraków, Poland.
| | | | | |
Collapse
|
8
|
Yoshii N, Iwahashi K, Okazaki S. A molecular dynamics study of free energy of micelle formation for sodium dodecyl sulfate in water and its size distribution. J Chem Phys 2007; 124:184901. [PMID: 16709133 DOI: 10.1063/1.2179074] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Free energy of micelle formation has been evaluated for spherical sodium dodecyl sulfate (SDS) in water by a thermodynamic integration method combined with a series of large-scale molecular dynamics calculations following the chemical species model. In particular, free energy change delta mu(n+1)0 with respect to the addition of one surfactant molecule to the spherical micelle of size n was obtained as a function of n. The free energy profile showed a minimum followed by a maximum, which corresponds to a peak in the size distribution. The calculated peak size n = 57 near its critical micelle concentration is in good agreement with the experimental averaged aggregation number n = 55-75 of the SDS micelle. The distribution showed a rather sharp peak, indicating that the size is almost a monodisperse one. The size is likely to be insensitive to the total concentration of the surfactant.
Collapse
Affiliation(s)
- Noriyuki Yoshii
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
| | | | | |
Collapse
|
9
|
Yoshii N, Okazaki S. Free energy of water permeation into hydrophobic core of sodium dodecyl sulfate micelle by molecular dynamics calculation. J Chem Phys 2007; 126:096101. [PMID: 17362132 DOI: 10.1063/1.2464000] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Noriyuki Yoshii
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
| | | |
Collapse
|
10
|
Yoshii N, Okazaki S. A molecular dynamics study of structural stability of spherical SDS micelle as a function of its size. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.05.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
11
|
Christopher PS, Oxtoby DW. Classical density functional study of mixed amphiphile mesostructures. J Chem Phys 2004; 121:5005-11. [PMID: 15332937 DOI: 10.1063/1.1782134] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This paper presents a density functional study of mixed amphiphile solutions. The amphiphiles are modeled using four to seven fused hard spheres where the connectivity is such that the amphiphiles have a proper head group. We present calculations of lamellar and vesicle density distributions, paying particular attention to the morphology of the bilayer structures.
Collapse
Affiliation(s)
- P S Christopher
- The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | | |
Collapse
|
12
|
Cao D, Wu J. Density functional theory for semiflexible and cyclic polyatomic fluids. J Chem Phys 2004; 121:4210-20. [PMID: 15332969 DOI: 10.1063/1.1774983] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effects of bond angle and chain stiffness on the structures of semiflexible polyatomic fluids are investigated by incorporating the bending potential into a density functional theory [Y. X. Yu and J. Z. Wu, J. Chem. Phys. 117, 2368 (2002)] that combines a modified fundamental measure theory for the excluded-volume effects and the first-order thermodynamics perturbation theory for the chain connectivity. The refined density functional theory faithfully reproduces the density profiles and conformational properties of a variety of triatomic fluids near a hard wall in which extensive Monte Carlo simulation data are available. In particular, the theory is able to capture the structures of rigid cyclic trimers where all segments are identical. The variation of local density profiles with respect to the chain length of confined polyatomic fluids is also explored. For quadratomic fluids confined in slit pores, the density profile of the middle segments exhibits novel double peaks that are absent in a fully flexible chain model. In addition, the density functional theory is applied to predicting the conformational properties and adsorption behavior of heterogeneous triatomic fluids of type "ABB" mimicking surfactant molecules. The competition between surface adsorption and self-association of trimers consisting of surface active and self-binding "A" segments and neutral "B" segment is explored.
Collapse
Affiliation(s)
- Dapeng Cao
- Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA
| | | |
Collapse
|