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(physical chemistry)



a layer of a substance 1 molecule thick on a surface or at a phase boundary. Monolayers are produced by adsorption, surface diffusion, and evaporation of a solvent from a solution containing a nonvolatile component. Monolayers that are formed by surface-active substances on the surface of a liquid or at the boundary between two nonmiscible liquids may exist in various two-dimensional states (gaseous, condensed, and intermediate, or “liquid-expanded”).

In gaseous monolayers, the distance between the molecules is great relative to their size; therefore, cohesive molecular interactions are virtually absent. On the other hand, condensed monolayers have limiting molecular packing density. In the case of fatty acids, alcohols, and other molecules that may be represented as hydrocarbon chains with a polar terminal group, condensed monolayers resemble “picket fences” occupying the entire surface area. Each molecule in such a “fence” is arranged perpendicularly or at an angle to the phase boundary surface and, regardless of its own length, usually occupies an area of 20–25 square angstroms. As a rule, linear macromolecular compounds form monolayers with horizontal orientation of the macromolecules. If the cohesion is sufficiently high, monolayers may have surface viscosity and strength that differ sharply from those of the bulk phases.

The structure and properties of monolayers have a strong effect on mass transfer (evaporation and diffusion), catalysis, friction, adhesion, and corrosion; this is taken into account in solving various engineering and industrial problems. The stability of highly disperse systems (sols, emulsions, and suspensions) often depends predominantly on the state of a monolayer.

Monolayers also play an important role in biological systems. For example, there are membrane structures in all cells of living organisms. Biological membranes basically consist of two monolayers of protein molecules with a double (bimolecular) layer of lipids between them. The thickness of such a four-layer membrane is 70–80 angstroms. The alternation of various types of monolayers also results in the lamellar structure of certain cell organelles, such as chloroplasts in the cells of green plants. Artificial monolayers are used as models of biological membranes in studying their structure and function.


Adamson, A. W. Physical Chemistry of Surfaces, 2nd ed. New York, 1971.
Gaines, G. L. Insoluble Monolayers at Liquid-Gas Interfaces. New York [1966].
Beredjick, N. “Issledovanie monomolekuliarnykh sloev polimerov.” In Noveishie melody issledovaniia polimerov. Moscow, 1966. Chapter 16. (Translated from English.)


References in periodicals archive ?
To engineer future devices, control them with light and create new properties through systematic modifications, we first need to understand the structural transformations of monolayers on the atomic level," said Stanford researcher Ehren Mannebach, the study's lead author.
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In general, the miscibility of the mixed polymer monolayers is determined from the plot of the mean areas at a constant surface pressure as a function of composition of one component in the binary mixture, lithe plot obeys a linear relationship, i.
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Liu Y, Shipton MK, Ryan J, Kaufman ED, Franzen S, and Feldheim DL; Synthesis, stability, and cellular internalization of gold nanoparticles containing mixed peptide-poly(ethylene glycol) monolayers.
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It looks at how the usability, durability and value-added of plastic packaging materials can be enhanced through nanotechnologies such as silicate nanoparticles, carbon nanofibres, carbon nanotubes, electrospun nanotubes, nanocapsules and self-assembled monolayers.
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As a first step, Kelly and his colleagues formed peptidomimetic monolayers on water.
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Self-assmebled monolayers (SAMs) for electrochemical sensing