Short-range non-electrostatic interactions

Polyelectrolyte adsorption is a subtle balance of electrostatic and short-range non-electrostatic interactions. For a given combination of charge density, segment charge and non-electrostatic interactions, this balance can be affected by changing the concentration of simple electrolytes [6]. 

The boundary conditions for f (x) depend on the nature of the short-range non-electrostatic interactions of the monomers and the surface. For simplicity, we take a nonadsorbing surface and require that the monomer concentration wQl vanish there ... 

The stability of the molecular conformation of organic solids Is determined by the nature and distribution within the molecular network of both covalent crosslinks and the various non-covalent Interactions. The latter Include localized (e.g. hydrogen bonds) and non-locallzed electrostatic Interactions and the short-range non-polar Interactions between molecular units due to the ubiquitous and weak van der Waals Induction and dispersion forces (7 ). 

Total contribution of short-range non-electrostatic solute-solvent interactions Gibbs free energy barrier in aqueous solution calculated as the AG(gas) value plus the electrostatic solvent shift determined by the SVPE calculation, without or with the non-electrostatic contributions determined by the PCM calculation... 

As seen in Table 2, the solvent effects are crucial for calculating realistic free energy barriers and, not surprisingly, the calculated solvent shifts are dominated by the solute-solvent electrostatic interactions. The estimated short-range non-electrostatic contributions to the free energy barriers are negligible compared to the electrostatic contributions to the solvent shifts. 

The concept of the vectorial coupling of quasispin momenta was first applied to the nucleus to study the short-range pairing nucleonic interaction [117]. For interactions of that type the quasispin of the system is a sufficiently good quantum number. In atoms there is no such interaction - the electrons are acted upon by electrostatic repulsion forces, for which the quasispin quantum number is not conserved. Therefore, in general, the Hamiltonian matrix defined in the basis of wave functions (17.56) is essentially non-diagonal. 

So far we have considered only interactions due to electrostatic structure of an ion. In addition to these there are also non-electrostatic interactions, generally short-ranged and repulsive, the most obvious of which are the excluded volume interactions due to the Pauli exclusion principle that prohibits two electrons from occupying the same quantum state [72]. 

Many different types of forces arise from molecule-molecule interaction. They may be electrostatic forces between permanent dipoles, induction forces between a permanent dipole and induced dipoles, or dispersion forces between non-polar molecules, etc. (Prausnitz, U2)). Forces involved in molecule-molecule interaction are known to be short-range in nature. 

The theories of polymer solutions upon which steric-stability theories are based are usually formulated in terms of a portmanteau interaction parameter (for example Flory s X Parameter and the excluded volume integral) which does not preclude electrostatic interactions, particularly under conditions where these are short range. It is thus appropriate to consider whether polyelect-roly te-stabilisation can be understood in the same broad terms as stabilisation by non-ionic polymers. It was this together with the fact that polyelectrolyte solutions containing simple salts show phase-separation behaviour reminiscent of that of non-ionic... 

Finally, it is interesting to note that the value of a for the poly-(metaphosphate) chain [Strauss and Wineman (241 )] has the same order of magnitude as those of non-electrolyte chains with substituents of comparable size. Under the observed theta-solvent conditions (0.415 M aqueous NaBr), the screened long range electrostatic interactions are just balanced by the various other contributions to the excluded volume effect, but there is no reason to expect a simultaneous obliteration of short-range electrostatic effects1. 

In vacuum, the long-range attractive van der Waals interactions as well as the short-range chemical forces are the predominant interaction between sample and tip (provided that electrostatic Coulomb interactions are carefully compensated or negligible and the tip is non-magnetic). The van der Waals forces are caused by the interaction of fluctuations in the electromagnetic field and are attractive when the tip approaches the surface, the chemical forces originate from Pauli-exclusion and nuclear-repulsion. The attraction increases until tip and sample have approximately the distance of a chemical bond. When distance between tip and surface is further decreased the interaction becomes repulsive (for more details see [83]). 

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