Contact Angles for Thin Lipid Films and the Determination of London-van der Waals Forces

Nature ◽  
1968 ◽  
Vol 217 (5130) ◽  
pp. 739-740 ◽  
Author(s):  
D. A. HAYDON ◽  
J. L. TAYLOR
Keyword(s):  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Contact Angles ◽  
Lipid Films

Van der Waals forces in oil–water systems from the study of thin lipid films - I. Measurement of the contact angle and the estimation of the van der Waals free energy of thinning of a film

1975 ◽  
Vol 347 (1649) ◽  
pp. 141-159 ◽  
Keyword(s):  
Free Energy ◽  
Van Der Waals ◽  
Monochromatic Light ◽  
Van Der Waals Forces ◽  
Contact Angles ◽  
Steric Interaction ◽  
Isotropic Layer ◽  
Free Energies ◽  
Lipid Film ◽  
Lipid Films

Free energies of formation of ‘black’ lipid films have been determined from measurements of their contact angles. The contact angles were calculated from the interference fringes formed in monochromatic light reflected from either the Plateau–Gibbs border or from lenses of bulk lipid solution trapped in the films. It is concluded that the electrostatic repulsion between the two surfaces of a film is negligibly small and that the ‘ steric’ interaction between the adsorbed monolayers of lipid molecules is of such short range that the free energy change during film formation originates almost entirely from work done by the van der Waals forces. The free energies determined for a range of different films all agree to within a factor of three with the free energy calculated from Lifshitz theory for water phases interacting across an isotropic layer of liquid hydrocarbon. Nevertheless, a systematic trend in the experimental data suggests that this picture of the lipid film is too simple and that either the polar groups of the lipid or the structure of the hydrocarbon region (or both) of the film have a significant influence on the results.

II.—The Van der Waals Force between a Proton and a Hydrogen Atom

1941 ◽  
Vol 61 (1) ◽  
pp. 20-25 ◽  
Author(s):  
C. A. Coulson
Keyword(s):  
Hydrogen Atom ◽  
Power Series ◽  
Interaction Energy ◽  
Van Der Waals ◽  
Ground States ◽  
Van Der Waals Forces ◽  
Van Der Waals Force ◽  
Hydrogen Atoms ◽  
Nuclear Separation

The calculation of Van der Waals forces has acquired considerable interest recently through the work of Buckingham, Knipp and others (Buckingham, 1937; Knipp, 1939). In these papers the interaction energy between two atoms is expressed as a power series in i/R, where R is the nuclear separation, and the various terms in this series are known as dipole-dipole, dipole-quadrupole, quadrupole-quadrupole, etc… interactions. In most cases only approximate values are obtainable for the coefficients in this series, though for two hydrogen atoms in their ground states, Pauling and Beach (1935) have determined the magnitudes correct to about I in 106. In this paper we discuss the simplest possible problem of this nature, i.e. the force between a bare proton and a normal unexcited hydrogen atom. We shall show that a rigorous determination of the coefficients in the power series can be made.

Determination of van der Waals Forces

Nature ◽  
1936 ◽  
Vol 138 (3480) ◽  
pp. 77-77 ◽  
Author(s):  
H. S. W. MASSEY ◽  
R. A. BUCKINGHAM
Keyword(s):  
Van Der Waals ◽  
Van Der Waals Forces

scholarly journals Free paths and transport phenomena in gases and the quantum theory of collisions. II.—The determination of the laws of force between atoms and molecules

1934 ◽  
Vol 144 (851) ◽  
pp. 188-205 ◽  
Keyword(s):  
Quantum Theory ◽  
Perturbation Method ◽  
Transport Phenomena ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Range Interaction ◽  
First Approximation ◽  
Diffusion Phenomena ◽  
The Law

The quantum theory has provided a means of calculating the interaction energies of two atoms by a perturbation method. It appears that, the short range interaction forces are due mainly to electron exchange phenomena between the two atoms, while the van der Waals forces arise from mutual polarization effects. The theory gives the first of these forces in the first approximation, while the van der Waals forces appear only in the second approximation, At large distances, where the interaction is small, it is somewhat surprising that the first approximation is not sufficient, and one is led to doubt the accuracy of the method when applied at distances at which the first and second approximations give comparable results. At these distances the mutual potential energy is comparable with the mean kinetic energy of a gas atom at ordinary temperatures, and it is therefore clear that a study of gas-kinetic collision phenomena should provide a satisfactory test of the validity of the perturbation method in this region. It is the object of this paper to carry out a number of calculations with this aim in view. In a previous paper the quantum theory of collisions was applied to gas-kinetic collisions, and it was shown that, although the classical theory can be used with accuracy to determine the law of force from viscosity and diffusion phenomena associated with heavy gases, it cannot he applied with safety to hydrogen and helium. The method to he used in such cases was given, and it was also shown that the existence of a definite total collision area—a feature of the quantum theory of scattering by a centre of force, the potential of which falls of more rapidly than r -2 at large distances—provides a further means of determining the law of force. As this collision area can now be directly measured with accuracy by molecular ray experiments, the range of applicability of tins method is considerably greater than that of methods based on transport phenomena.

Self-Assembly of a Chiral Cubic Three-Connected Net from the High Symmetry Molecules C60 and SnI4

2020 ◽  
Author(s):  
Daniel B. Straus ◽  
Robert J. Cava
Keyword(s):  
Organic Synthesis ◽  
Self Assembly ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
High Symmetry ◽  
Molecular Chirality ◽  
Chiral Materials ◽  
Self Assembled ◽  
Chiral Centers

The design of new chiral materials usually requires stereoselective organic synthesis to create molecules with chiral centers. Less commonly, achiral molecules can self-assemble into chiral materials, despite the absence of intrinsic molecular chirality. Here, we demonstrate the assembly of high-symmetry molecules into a chiral van der Waals structure by synthesizing crystals of C<sub>60</sub>(SnI<sub>4</sub>)<sub>2</sub> from icosahedral buckminsterfullerene (C<sub>60</sub>) and tetrahedral SnI4 molecules through spontaneous self-assembly. The SnI<sub>4</sub> tetrahedra template the Sn atoms into a chiral cubic three-connected net of the SrSi<sub>2</sub> type that is held together by van der Waals forces. Our results represent the remarkable emergence of a self-assembled chiral material from two of the most highly symmetric molecules, demonstrating that almost any molecular, nanocrystalline, or engineered precursor can be considered when designing chiral assemblies.

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