Physical and chemical aspects of the study of clusters, nanostructures and nanomaterials
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Temperature dependences of the molecular area of surfactant 2D monolayers at the air/water interface

E.S. Kartashynska

L.M. Litvinenko Institute of Physical Organic and Coal Chemistry

DOI: 10.26456/pcascnn/2022.14.408

Original article

Abstract: The dependences of the molecular area (Ac) at the onset of the transition from the liquid-expanded to liquid-condensed (LE-LC) phase for 2D surfactant monolayer on the temperature and chain length are considered for seven surfactant classes at the air/water interface. A thermodynamic model of the amphiphilic monolayer behavior (taking into account the nonideality of mixing entropy) is used to evaluate Ac, as well as a quantum chemical approach that allows an assessment of the thermodynamic and structural parameters of surfactant associates. The calculated Ac values adequately reflect the experimental temperature dependence for the considered phase transition: the temperature increase leads to a decrease of the area per surfactant molecule with the fixed chain length and vice versa lengthening of the surfactant carbon chain at a fixed temperature results to the Ac value increase. The average values of the slope in the Ac = f(T) dependences for the regarded surfactant classes are in the range of 0,57-1,32 Å2/°C. The estimation of the (dAc/dn)T value shows that the best agreement of the calculated and available experimental data is achieved for saturated carboxylic acids and dialkyl-substituted melamine. The obtained results demonstrate applicability of the proposed approach for predictive purposes.

Keywords: 2D monolayer, clusterization Gibbs energy, unit cell, phase transition, thermodynamic model

  • Elena S. Kartashynska – Dr. Sc., Researcher of Supramolecular Chemistry Department, L.M. Litvinenko Institute of Physical Organic and Coal Chemistry


Kartashynska, E.S. Temperature dependences of the molecular area of surfactant 2D monolayers at the air/water interface / E.S. Kartashynska // Physical and chemical aspects of the study of clusters, nanostructures and nanomaterials. — 2022. — I. 14. — P. 408-418. DOI: 10.26456/pcascnn/2022.14.408. (In Russian).

Full article (in Russian): download PDF file


1. Horn L.W., Gershfeld N.L. Equilibrium and metastable states in lecithin films, Biophysical Journal, 1977, vol. 18, issue 3, pp. 301-310. DOI: 10.1016/S0006-3495(77)85615-4.
2. Baret J.F., Bois A.G., Dupin J.J., Firpo J.L. The liquid-expanded and the liquid-condensed phases in amphiphile monolayers are separated by a second-order phase transition, Journal of Colloid Interface Science, 1982, vol. 86, issue 2, pp. 370-376. DOI:10.1016/0021-9797(82)90082-0.
3. Pallas N.R., Pethica B.A. Liquid-expanded to liquid-condensed transition in lipid monolayers at the air/water interface, Langmuir, 1985, vol. 1, issue 4, pp. 509-513. DOI: 10.1021/la00064a019.
4. Barzyk W., Lunkenheime K., Pomianowski A. Orientation phase transitions of undissociated n-decanoic acid at the air/solution interface revealed by surface pressure and electric potential, Advances in Colloid and Interface Science, 2018, vol. 259, pp. 1-20. DOI: 10.1016/j.cis.2018.06.003.
5. Kato T., Akiyama H., Tanaka T. direct evidence of the enthalpy release being accompanied by first-order phase transitions of monolayers at the air/water interface by compression, Chemical Physics Letters, 1991, vol. 184, issue 5-6, pp. 455-460. DOI: 10.1016/0009-2614(91)80018-S.
6. Jalal I., Zografi G. On the lack of a true thermodynamic transition between «liquid-expanded» and «liquid-condensed» fatty acid monolayer states, Journal of Colloid and Interface Science, 1979, vol. 68, issue 1, pp. 196-198. DOI: 10.1016/0021-9797(79)90272-8.
7. Ruckenstein E. On the nature of the liquid expanded/liquid condensed phase transition in monolayers of polar moleculesб Journal of Colloid and Interface Science, 1997, vol. 196, issue 2, pp. 313-315. DOI: 10.1006/jcis.1997.5197.
8. Vysotsky Yu.B., Fomina E.S., Belyaeva E.A. et al. Temperature effect on the monolayer formation of substituted alkanes at the air/water interface: a quantum chemical approach, Journal of Physical Chemistry B, 2012, vol. 116, issue 30, pp. 8996−9006. DOI: 10.1021/jp303617n.
9. Vollhardt D., Fainerman V.B., Siegel S. Thermodynamic and textural characterization of DPPG phospholipid monolayers, Journal of Physical Chemistry B, 2000, vol. 104, issue 17, pp. 4115-4121. DOI: 10.1021/jp992529s.
10. Fainerman V.B., Vollhardt D., Melzer V. Equation of state for insoluble monolayers of aggregating amphiphilic molecules, Journal of Physical Chemistry, 1996, vol. 100, issue 38, pp. 15478-15482. DOI: 10.1021/jp960523m.
11. Fainerman V.B., Vollhardt D. Equation of state for the phase coexistence region of insoluble monolayers under consideration of the entropy nonideality, Journal of Physical Chemistry B, 2008, vol. 112, issue 5, pp. 1477-1481. DOI: 10.1021/jp077372f.
12. Vysotsky Yu.B., Kartashynska E.S., Belyaeva E.A. et al. Сomputational quantum chemistry applied to monolayer formation at gas/liquid interfaces, Computational methods for complex liquid-fluid interfaces, ed. by M. Karbaschi, R. Miller M.T. Rahni. Boca Raton, CRC Press, 2015, chapter 10, pp. 199-249. DOI: 10.1201/b19337.
13. Kartashynska E.S., Vollhartd D. Quantum chemical assessment of the molecular area corresponding to the onset of the LE–LC phase transition for amphiphilic 2D monolayers at the air/water interface, Physical Chemistry Chemical Physics, 2021, vol. 23, pp. 25356-25364. DOI: 10.1039/d1cp03511h.
14. Smith T. Monolayers on water: I. A theoretical equation for the liquid expanded state, Journal of Colloid and Interface Science, 1967, vol. 23, issue 1, pp. 27-35. DOI: 10.1016/0021-9797(67)90081-1.
15. Rettig W., Kuschel F. A first-order transition between the liquid-expanded and the liquid-condensed phases in insoluble monolayers of fatty acid esters as detected by measurement of equilibrium spreading pressure, Journal of Colloid and Interface Science, 1990, vol. 140, issue 1, pp.169-174. DOI: 10.1016/0021-9797(90)90332-I.
16. Islam N., Kato T. Influence of temperature and alkyl chain length on phase behavior in langmuir monolayers of some ethoxylenated nonionic surfactants, Journal of Colloid and Interface Science, 2006, vol. 294, issue 2, pp. 288-294. DOI: 10.1016/j.jcis.2005.07.023.
17. Lunkenheimer K., Barzyk W., Hirte R., Rudert R. Adsorption properties of soluble, surface-chemically pure n-alkanoic acids at the air/water interface and the relationship to insoluble monolayer and crystal structure properties, Langmuir, 2003, vol. 19, issue 15, pp. 6140–6150. DOI: 10.1021/la034379p.
18. Gershfeld N. The liquid condensed/liquid expanded transition in lipid films: a critical analysis of the film balance experiment, Journal of Colloid and Interface Science, 1982, vol. 85, issue 1, pp. 28-40. DOI: 10.1016/0021-9797(82)90232-6.
19. Halperin K., Ketterson J.B., Dutta P. A study of the mechanical behavior of surface monolayers using orthogonal Wilhelmy plates, Langmuir, 1989, vol. 5, issue 1, pp. 161-164. DOI: 10.1021/la00085a030.
20. Moore B.G., Knobler C.M., Akamatsu S., Rondelez F. Phase diagram of Langmuir monolayers of pentadecanoic acid: uantitative comparison of surface pressure and fluorescence microscopy results, Journal of Physical Chemistry, 1990, vol. 94, issue 11, pp. 4588-4595. DOI: 10.1021/j100374a042.
21. Baret J.F., Hasomonay H., Firpo J. L., Dupin J. J., Dupeyrat M. The different types of isotherm exhibited by insoluble fatty acid monolayers. A theoretical interpretation of phase transitions in the condensed state, Chemistry and Physics of Lipids, 1982, vol. 30, issue 2-3, pp. 177-187. DOI: 10.1016/0009-3084(82)90051-2.
22. Vollhardt D., Fainerman V.B., Liu F. Thermodynamic and structural characterization of amphiphilic melamine-type monolayers, Journal of Physical Chemistry B, 2005, vol. 109, issue 23, pp. 11706-11711. DOI: 10.1021/jp050796u.
23. Fomina, E.S.; Vysotsky, Yu. B.; Vollhardt, D.; Fainerman, V. B.; Miller, R. Quantum chemical analysis of the thermodynamics of 2D cluster formation of 2-hydroxycarboxylic acids at the air/water interface. Soft Matter, 2013, vol. 9, pp. 7601-7616. DOI: 10.1039/C3SM51094H.

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