Monopolar interactions

MONOPOLAR INTERACTIONS, IONIC-FLUCTUATION FORCES, BETWEEN SMALL CHARGED PARTICLES... 

Figure 4.45 Three main types of hyperfine interactions a monopolar interaction, b electric quadrupolar interaction and c magnetic dipolar interaction. Adapted from [138]...

Wisniewska, A., J. Widomska, and W. K. Subczynski. 2006. Carotenoid-membrane interactions in liposomes Effect of dipolar, monopolar, and nonpolar carotenoids. Acta Biochim. Polonica 53 475 184. 

If the defects can be considered point charges, localized on their own lattice sites, the polar electrostatic interaction between them is usually written as a long range monopolar Coulomb energy. If, on the other hand, for large concentrations of defects, local charge effects, as described in the introduction, are present, then AHjnter is much more difficult to write. 

But let us now inspect the Yu values for the various chemicals given in Table 3.2. As we would probably have expected intuitively from our discussions in Section 3.2, Yu values close to 1 are found in those cases in which molecular interactions in the solution are nearly the same as in the pure liquid compound. For example, when the intermolecular interactions in a pure liquid are dominated by vdW interactions, and when solutions also exhibit only vdW interactions between the solute and solvent and between the solvent molecules themselves, we have Yu values close to 1. Examples include solutions of nonpolar and monopolar compounds in an apolar solvent (e.g., n-hexane, benzene, and diethylether in hexadecane), as well as solutions of nonpolar solutes in monopolar solvents (e.g., n-hexane in chloroform). In contrast, if we consider situations in which strong polar interactions are involved between the solute... 

Finally, inspection of Table 3.2 shows also that there are cases in which Yu can be even smaller than 1. An example is a solution of diethylether in chloroform. Here, the solute is an electron donor (H-acceptor), while the chloroform solvent is an electron acceptor (H-donor). In this case, the solute and solvent both acquire additional inter-molecular interactions that were unavailable to them in their pure liquid forms. The monopolar diethylether (only vdW interactions in its pure liquid) can add polar interactions to its vdW attractions with the molecules of the monopolar chloroform solvent exhibiting a complementary electron acceptor property. 

A very different picture is found for the compounds in hexadecane. Here, the apolar and monopolar compounds show almost ideal behavior (i.e., Gj 0) because in their own liquids, as well as in hexadecane, they can undergo only vdW interactions. In the case of ethanol, again, a significant enthalpy cost and entropy gain is found, which can be explained with the same arguments used above for the gas phase. The absolute Hff and T-Sf( values are, however, smaller as compared to the gas phase, because ethanol undergoes vdW interactions with the hexadecane-solvent molecules, and because the freedom to move around in hexadecane is smaller than in the gas phase. 

For monopolar compounds (e.g., ethers, ketones, aldehydes), Aaw//, may even be larger than A f/(.. This happens because of the additional polar interactions in the aqueous phase, leading to negative H%, values (Table 5.3). 

Some nonionic organic compounds exhibit much stronger mineral surface affinities than we see for apolar and weakly monopolar compounds like chlorobenzenes and PAHs. In these cases, the organic sorbates are able to displace water from the mineral surface and participate in fairly strong sorbate sorbent intermolecular interactions. Example compounds include mtroaromatic compounds (NACs) such as the explosive, trinitrotoluene (TNT), or the herbicide, 2,4-dinitro-6-methyl-phenol, also called dinitro-o-cresol (DNOC). 

There are monopolar fluctuations of the net charge on the colloid and its surrounding solution there are dipolar fluctuations, the first moment of the ionic-charge distribution around the colloid as well as polarization of the colloid itself. Monopolar and dipolar fluctuations couple to create a hybrid interaction, d-m, again in the limit of the n = 0 sampling frequency at which the ions are able to fluctuate. The salt solution screens even the dipolar fluctuation the same way that the low-frequency-fluctuation term is screened in planar interactions. For dielectric spheres of radius a, ss whose incremental contribution to dielectric response is a =... 

Not only are there fluctuations in the electric fields that create the dipolar fluctuations of most van der Waals forces but there are also fluctuations in electric potential with concomitant fluctuations in the number density of ions and the net charge on and around these small spheres. Monopolar charge-fluctuation forces occur when ion fluctuations in the spheres differ from ion fluctuations in the medium. Perhaps it is better to say that these forces occur when ion fluctuations around the suspended particles differ from what they would have been in the solution in the absence of particles. To formulate these interactions, we allow the ionic population of the spheres to equilibrate with the surrounding salt solution and to exchange ions with that surrounding solution. Then we compare the ionic fluctuations that occur from the presence of the small spheres with those in their absence. To do this we must have a way to count the number of extra ions associated with each sphere compared with the number of ions in their absence. 

If both y and y are present to interact, the substance is termed bipolar. If one of them is not present (equals zero), the substance is termed monopolar. If both y and y are absent,... 

Amphoters are those species whieh bear both acidic and basic sites and can thus interact specifically with either pure aeids or bases. In the terminology of van Oss et al. [22] pure acids and bases are called monopolar whereas amphoters are called bipolar. This is a rather unfortunate terminology since acid-base interactions are distinguished from polar interactions. For this reason, Berg [16] preferred the terms monofunc-tional for pure acids and pure bases, and bifunctional for amphoters. 

In the monopolar model, dipole moments are substituted by the partial charges located on each atom of the molecule. The total interaction energy is then calculated as one half of the sum over all the couples of atomic partial charges according to... 

In a large part of the (current) literature the Lifshitz-van der Waals component (o, is simply termed dispersion component and the Lewis acid-base interactions (o ) are interpreted as polar interactions even though the material s dipole moments may be zero or the interactions originating from permanent dipoles are very small and can be easily associated with the dispersion part [6]. The misleading denominations go back to a historical misidentification of the acid-base interactions as polar interactions in the Owens-Wendt-Rabel-Kaelble [7-9] approach to calculate the IFT [6] (OWRK model). However, as an impact on the SFE calculation by this misinterpretation of this old theory occurs only when a monopolar base interacts with a monopolar acid, this nomenclature is still widely used. And here in this work we will also use the terms dispersion and po/ar interactions to differentiate the two major contributions to SFE, ST, and IFT. For a detailed discussion of the use of contact angles in determining SFE of solids and other methods of determining SFE, see Etzler [10]. 

Minimization of the harmful interaction of stray currents connected with the work of a monopolar HVDC line is based on the application of ground or maritime electrodes of small resistance. This is why they are of large dimensions and located in environments of small resistivity. Bipolar systems should be exploited in such a way that leakage of equalizing currents to the ground does not occur (Nikolakakos, 1998). 

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