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<p>The study reports results from the quantum chemical assessment of the spontaneous monolayer formation of fatty alcohols C<sub>n</sub>H<sub>2n+1</sub>OH (<i>n</i> = 6 − 14) at the graphene-like surface modeled by polyaromatic hydrocarbon (PAH) within the PM6-DH2 method. Unlike monolayers of alkanes, lamellae of alcohols on graphene form a herringbone pattern due to the presence of hydrogen O···H–O bonds between the hydroxyl groups of two interacting surfactant molecules belonging to neighboring lamellae. Calculations of the thermodynamic parameters of binding for alcohol monomers and dimers with tricircumcoronene have shown that the intermolecular interactions of the terminal fragments of surfactants make a destabilizing contribution to the Gibbs energy of the alcohol association during the formation of a monolayer on a graphene surface. However, C–H···π interactions between CH<sub>2</sub> fragments of the alcohol chain and condensed PAH rings are stabilizing, contributing −4.77&#xa0;kJ/mol. Their significant advantage is partially countervailed by the formation of energetically unfavorable CH···HC interactions of the “e” type between the hydrocarbon chains of interacting alcohol molecules. It results in the existence of a threshold length of the alcohol chain, starting from which these compounds are capable of crystalline monolayer formation on graphene-like surfaces. Spontaneous film formation of <i>n</i>-alcohols on graphene at 298&#xa0;K is possible for surfactants possessing no less than10 carbon atoms in the chain. An increase in the chain length of alcohols by one methylene fragment is equivalent to an increase in the temperature of the film formation in the range from 6 to 22&#xa0;°C for alcohols from pentanol to octadecanol, following experimental data.</p>

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Thermodynamics and structure of 2D aliphatic alcohol monolayers on graphene within semi-empirical quantum chemical approach

  • 期刊论文

  • 发表日期：

    2025年3月26日

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  • Elena S. Kartashynska

摘要

The study reports results from the quantum chemical assessment of the spontaneous monolayer formation of fatty alcohols CnH2n+1OH (n = 6 − 14) at the graphene-like surface modeled by polyaromatic hydrocarbon (PAH) within the PM6-DH2 method. Unlike monolayers of alkanes, lamellae of alcohols on graphene form a herringbone pattern due to the presence of hydrogen O···H–O bonds between the hydroxyl groups of two interacting surfactant molecules belonging to neighboring lamellae. Calculations of the thermodynamic parameters of binding for alcohol monomers and dimers with tricircumcoronene have shown that the intermolecular interactions of the terminal fragments of surfactants make a destabilizing contribution to the Gibbs energy of the alcohol association during the formation of a monolayer on a graphene surface. However, C–H···π interactions between CH2 fragments of the alcohol chain and condensed PAH rings are stabilizing, contributing −4.77 kJ/mol. Their significant advantage is partially countervailed by the formation of energetically unfavorable CH···HC interactions of the “e” type between the hydrocarbon chains of interacting alcohol molecules. It results in the existence of a threshold length of the alcohol chain, starting from which these compounds are capable of crystalline monolayer formation on graphene-like surfaces. Spontaneous film formation of n-alcohols on graphene at 298 K is possible for surfactants possessing no less than10 carbon atoms in the chain. An increase in the chain length of alcohols by one methylene fragment is equivalent to an increase in the temperature of the film formation in the range from 6 to 22 °C for alcohols from pentanol to octadecanol, following experimental data.