Conformation peculiarities of gemini surfactant monomers for 2D monolayer formation at the liquid/fluid interface
E.S. Kartashynska 1,2
1 L.M. Litvinenko Institute of Physical Organic and Coal Chemistry
2 Donetsk National Technical University
Abstract: The present work is devoted to the consideration of gemini surfactant monomers with a nonionic hydrophilic part and a different structure of the spacer connecting the hydrocarbon chains. It is possible to single out two conditional conformations of monomers depending on the spacer type: with an «extended» and «compact» spacer in the case of a flexible etoxylated or hydrocarbon chain, and only with the «extended» rigid spacer in the case of aromatic ring in it. The length for all three types of spacers in the case of their «extended» conformation is approximately the same for the considered bis-surfactants and allows two hydrocarbon molecules to be vertically introduced into the resulting cavity. The «compact» conformation of flexible spacers ensures the implementation of intramolecular CH‧‧‧HC interactions between hydrocarbon chains, which are not carried out in monomers with «extended» one. The thermodynamic parameters of formation for the found monomer conformations are calculated. For gemini surfactant conformers, the formation of structures with a «compact» spacer is more advantageous according to the Gibbs energy due to the formation of intramolecular CH‧‧‧HC interactions between hydrophobic chains of the amphiphilic compound. Comparison of the contributions of intramolecular CH‧‧‧HC interactions to the formation enthalpy and entropy of bis-surfactants with an etoxylated bridge in a «compact» conformation reveals good agreement with the similar contributions of intermolecular ones for dioxyethylated alcohols. It shows the same nature of CH‧‧‧HC interactionns realizing both inside a molecule with two hydrocarbon chains and between two surfactant molecules with single hydrocarbon chain.
Keywords: gemini surfactants, monomer, enthalpy, absolute entropy, Gibbs energy of formation, CH‧‧‧HC interactions
- Elena S. Kartashynska – Dr. Sc., Senior Researcher of Supramolecular Chemistry Department, L.M. Litvinenko Institute of Physical Organic and Coal Chemistry, professor of the department of general, physical and organic chemistry Donetsk National Technical University
Kartashynska, E.S. Conformation peculiarities of gemini surfactant monomers for 2D monolayer formation at the liquid/fluid interface / E.S. Kartashynska // Physical and chemical aspects of the study of clusters, nanostructures and nanomaterials. — 2023. — I. 15. — P. 412-423. DOI: 10.26456/pcascnn/2023.15.412. (In Russian).
Full article (in Russian): download PDF file
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