Effect of Pressure on Dry and Hydrated Self Assembled Monolayers: A Molecular Dynamics Simulation Study

Abstract:

Molecular dynamics simulation was used to study the effect of pressure on self-assembled monolayers (SAM) of n-alkanethiols [(CH₃(CH₂) n-1, n=14, 15] on Au (111) for dry systems and in the presence of water. The stress-strain behavior and effects of compression on structural characteristics under various normal pressures have been investigated. We found the effect of compression on tilt and tilt orientation angles for dry and hydrated SAM system. Furthermore, a comparison of the results obtained for tilt and tilt orientation angles for hydrated C14 and C15 indicates a more stable structure for C15 (an odd system) under high pressures. We also found excellent elastic recovery of SAM monolayers with and without water is evidence of their exceptional potential to be used under compression in various conditions. Young’s moduli are calculated for various systems under uniaxial compression.

• Periodical: Applied Mechanics and Materials (Volume 553)
• Pages: 35-40
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.553.35
• Online since: May 2014
• Authors: Leyla Ramin*, Ahmad Jabbarzadeh
• Keywords: Molecular Dynamics Simulation, Self-Assembled Monolayers, Stress-Strain, Young's Modulus

References

[1] Porter, M. D.; Bright, T. B;. Allara, D. L; and Chidsey, C. E. D.; Spontaneously organized molecular assemblies. 4. Structural characterization of n-alkyl thiol monolayers on gold by optical ellipsometry, infrared spectroscopy, and electrochemistry, J. Am. Chem. Soc., (1987).

DOI: 10.1021/ja00246a011

[2] McDermott, M.; Green, J. & Porter, M. Scanning force microscopic exploration of the lubrication capabilities of n-alkanethiolate monolayers chemisorbed at gold structural basis of microscopic friction and wear. Langmuir, (1997).

DOI: 10.1021/la962099m

[3] Tsukruk, V. Molecular lubricants and glues for micro- and nanodevices. Advanced Materials, (2001) 13, 95-108.

DOI: 10.1002/1521-4095(200101)13:2<95::aid-adma95>3.0.co;2-j

[4] Hautman, J.; Klein, M. L.; Simulation of a monolayer of alkyl thiol chains, Journal of Chemical Physics, (1989), 91, 4994-5001.

DOI: 10.1063/1.457621

[5] Siepmann, J.L.; Martin, M.C.; Mundy C.J.; Klein, M.L.; Intermolecular potentials for branched alkanes and the vapour-liquid phase equilibria of n-heptane, 2-methylhexane, and 3-ethylpentane, Mol. Phys., (1997), 90, 687-693.

DOI: 10.1080/00268979709482654

[6] Jabbarzadeh, A.; Tanner, R.I.; Flow-induced crystallization: unravelling the effects of shear rate and strain, Macromolecules, 2010, 43, 8136–8142.

DOI: 10.1021/ma100985x

[7] A. Jabbarzadeh, P. Harrowell, R.I. Tanner, J. Chem Phys, 125, 034703 (2006).

[8] Ramin, L.; Jabbarzadeh, A., Frictional properties of two alkanethiol self assembled monolayers in sliding contact: Odd-even effects, J. Chem. Phys., (2012), 137, 174706-174721.

DOI: 10.1063/1.4764301

[9] Ramin, L.; Jabbarzadeh, A., Effect of compression on self assembled monolayers: a molecular dynamics study, Modell. Simul. Mater. Sci. Eng., 2012, 20, 085010-085035.

DOI: 10.1088/0965-0393/20/8/085010

[10] Ramin, L.; Jabbarzadeh, A., Effect of load on structural and frictional properties of alkanethiol self-assembled monolayers on gold: Some odd-even effects, Langmuir, 2012, 28, 4102–4112.

DOI: 10.1021/la204701z

[11] Ramin, L.; Jabbarzadeh, A., Odd-even effects on the structure, stability, and phase transition of alkanethiol self-assembled monolayers, Langmuir, 2011, 27, 9748-59.

DOI: 10.1021/la201467b

[12] Henda R, Grunze M M and Pertsin A J 1998 Tribology Letters 5 191–195.

DOI: 10.1023/a:1019141708230

[13] Oncins G, Vericat C and Sanz F 2008 The Journal of Chemical Physics 128 No. 044701.

[14] Price W J, Leigh S A, Hsu S M, Patten T E and Liu G Y 2006 J. Phys. Chem. A 110 1382-1388.

[15] Joyce S A, Thomas R C, Houston J E, Michalske T A and Crooks R M 1992 Physical review letters 68 2790-2793.

DOI: 10.1103/physrevlett.68.2790

[16] Houston J E and Kim H I 2002 Acc. Chem. Res. 35 547-553.