Functional modular dynamic model of the surface layer of water

Abstract

It was demonstrated that it is impossible to develop a universal model of a connected surface layer (SL) that would be applicable to all liquids. It was established that the degree of connectivity of the structure of the SL, a characteristic that determines its stability and the value of the surface tension it creates, depends on the stereochemical parameters of the constituent atoms and molecules (the valence angles and coordination numbers in connected structures composed of similar species). The use of the concept of the module, which underlies the description of the connectivity of stable solid structures, including crystals, in conjunction with the symmetrical assembly method, made it possible to develop an ultimately ordered two-dimensional crystalline model (approximant) of the connected structure of an ∼5-A SL of water composed of unitary modular building blocks. An invariant in the form of a network of water molecules with free H-bonds was identified. This invariant governs the interaction of the SL with hydrophilic groups of surfactants and polymers. The specifics of the structure of the SL of water entirely determines its functional properties, such as the superplasticity, high conductivity, polarization of its sides, permeability to ions and gas molecules, perfect wettability (or nonwettability) of some substances, etc. The mechanisms operative at the different stages of the cooperative transformation of the structure of the water SL approximant during its interaction with surfactant molecules, up to the formation of the final form of the Langmuir monolayer, were considered. For each stage of the transformation of the approximant under the action of surfactant molecules and the external compression pressure during the formation of the monolayer, the surface area per surfactant molecule was calculated. The proposed approach makes it possible to treat the formation of Langmuir monolayers in a way that differs from the commonly accepted one.