Polar intermolecular force definition

Van der Waals forces represent important intermolecular interactions between nonelectrolyte substances, and can be categorized into dipole-dipole, dipole-induced-dipole, and induced-dipole-induced-dipole forces. Polar molecules, by definition, will have a permanent dipole moment, and will interact with the oppositely charged portions or other molecules having permanent dipole moments. The dipole-dipole interaction is known as the orientation effect, or as the Keesom force. 

Parameters which encode certain structural features and properties are needed to correlate biological activities with chemical structures in a quantitative manner. Of special value are physicochemical properties which are directly related to the intermolecular forces involved in the drug-receptor interaction as well as to the transport and distribution properties of drugs. In this respect hydrophobic, polar, electronic, and steric properties are most important most often, polarizability parameters are considered as being closely related to steric parameters and are discussed together with these parameters, although they are definitely different (if structural variation is appropriate). 

From the definitions of Wa and Wq, it can be seen that is a function of surface energies. If the structure of a material and the molecular potential energy-separation relationships are known, the surface energy can be calculated by evaluating the work required to separate to infinity the material either side of a chosen plane. For a material in which the dominant intermolecular forces are dispersion force interactions, the Lennard-Jones potential (see Dispersion forces and Polar forces) will apply, and the calculation is relatively simple. It gives work of cohesion on phase 1... 

Adhesion, by its definition, depends on the ability of two unlike phases to hold themselves together across a common interface. Physical adhesion must first take place before any other bonding processes such as chemical reaction can occur, and such physical adhesion depends on the strength of intermolecular force interaction, on the area of contact and on the distance separating the atoms forming the top layer of each surface (see Dispersion forces, polar forces). When both phases are undeformable, such as with two solids that are not atomically smooth, poor adhesion results because an insufficient area of each surface is in atomic contact with the other. When one phase is deformable, such as with a liquid of low viscosity, physical adhesion takes place at all parts of the surface. Physical adhesion with a liquid in contact with a solid leads to spreading and wetting processes that now depend on the competition of adhesion forces with cohesion forces within the liquid. 

The idea of solvent polarity refers not to bonds, nor to molecules, but to the solvent as an assembly of molecules. Qualitatively, polar solvents promote the separation of solute moieties with unlike charges and they make it possible for solute moieties with like charges to approach each other more closely. Polarity affects the solvent s overall solvation capability (solvation power) for solutes. The polarity depends on the action of all possible, nonspecific and specific, intermolecular interactions between solute ions or molecules and solvent molecules. It covers electrostatic, directional, inductive, dispersion, and charge-transfer forces, as well as hydrogen-bonding forces, but excludes interactions leading to definite chemical alterations of the ions or molecules of the solute. 

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