Molecular dynamics study of salt effects on micellization of N-dodecyl-N,N-dimethyl-3-ammonio-1-propane-sulfonate

ABSTRACT

In this paper, molecular dynamics simulation methods were used to investigate salt effects on micellization of N-Dodecyl-N,N-Dimethyl-3-Ammonio-1-Propane-sulfonate (SB12-3) in aqueous solution. It is proved that micelle shapes transform from spherical to prolate spherical shape after 30.0 ns simulation with different NaCl and CaCl₂ concentration. By comparison with the eccentricity value without salt addition, SB12-3 shows salt tolerance behaviors due to its unique “inner salt” structure of amphiphilic surfactant. Radial distribution function (RDF), hydrophobic groups solvent accessible surface area (SASA), hydrogen bond, and the deuterium order parameter (S_CD) are to elucidate salt effects on SB12-3 micelle formation. The radius of micelle is achieved by the related RDF value and in accordance with other researches. The addition of NaCl and CaCl₂ didn’t change the structure of micelle significantly and have little effects on the interactions between SB12-3 and water molecule. By comparison with the results without salt system, SASA of hydrophobic groups is almost the same, and SASA of hydrophilic groups and total molecule fluctuates only slightly. This further indicates that the surface of micelles is more hydrophilic due to the strong interactions between SB12-3 and water molecules. The existence of NaCl and CaCl₂ will enhance the hydrophilic interactions.

GRAPHICAL ABSTRACT

KEYWORDS:

• Calcium chloride
• micelle formation
• molecular dynamic simulation
• N-dodecyl-N,N-dimethyl-3-ammonio-1-propane-sulfonate
• sodium chloride

Acknowledgment

Xiang Gao is gratefully acknowledged for his generous technical assistance and fruitful discussions.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 51674085). We thank the support of this work by grants foundation program of Northeast Petroleum University (NEPUPY-1-11), Nanjing Polytechnic Institute (NHKY-2017-04 and Beidou Research Plan), and University of Natural Science Foundation in Jiangsu Province (NO.16KJB530006).