Coulomb noncovalent interactions

Coulombic interactions are among the most widely encountered noncovalent interactions in polymeric systems that are rivaled only by hydrogen bonding and van der Waals interactions in their frequency (Paul and Antonietti 2003). The most important example of using coulombic interactions in materials science is in the field of ionomers, which are tailor-made materials. lonomers are widely used... 

Nair KP, Week M. Noncovalently functionalized poly(norbomene)s possessing both hydrogen bonding and coulombic interactions. Macromolecules 2007 40 211-219. 

The essential realization in this spontaneous ordering process is the importance of noncovalent bonding interaction between molecules, that is, supramolecular chemistry. These conformation-specific interactions are governed by weak forces including hydrogen bonding, metal coordination, van der Waals forces, pi-pi interactions, and electrostatic Coulombic effects. The cooperative action of multiple noncovalent interaction forces is precisely the path nature takes to produce shape and form. 

The LMWGs have in common the property that they self-assemble into fibrous aggregates a process that can be driven by different noncovalent interactions like coulomb interactions, hydrogen bonding, n-n interactions, van der Waals forces, and solvophobic effects. For most of the early examples of LMWGs, the gelation prop-... 

The belief that electrostatic (Coulomb) interactions exhibit little directionality (i.e., that their energy hardly depends on the bond angle) is widespread. This is because the concept of net atomic charges (atom-centered monopoles) has become ingrained in chemists thinking, so that Coulomb interactions with a polar atom are believed to be necessarily isotropic and directionahty of Coulomb interactions only to be the result of secondary interactions with more distant atoms. Neither of these assumptions is correct and the reasons have been known for decades. Nonetheless, directionality in noncovalent interactions is still often attributed to covalent contributions or donor-acceptor interactions because the Coulomb interaction is believed not to be able to give rise to significant directionality. The purpose of this chapter is to discuss Coulomb interactions with special emphasis on directionality and anisotropy of the molecular electrostatic potential (MEP) [1] around atoms. 

Interactions become shorter-ranged and weaker as higher multipole moments become involved. When a monopole interacts with a monopole. Coulomb s law says u r) oc r But when a monopole interacts with a distant dipole, coulombic interactions lead to u r) oc r (see Equation (21.26)). Continuing up the multipole series, two permanent dipoles that are far apart interact as u(r) oc r Such interactions can be either attractive or repulsive, depending on the orientations of the dipoles. Table 24.2 gives typical energies of some covalent bonds, and Table 24.3 compares covalent to noncovalent bond strengths. 

It follows from the Hellmann-Feynman theorem1,2 that these interactions are essentially Coulombic, and hence can be described accurately in terms of classical electrostatics, given the correct charge distributions. This has been discussed by Hirschfelder et al.3 4 The problem, with regard to solute-solvent interactions, is one of scale, i.e., the large number of molecules of the solvent that must be taken into account in order to realistically represent its effects. Thus, whereas interaction energies of relatively small noncovalently-bound complexes are... 

The alternative noncovalent functionalization does not rely on chemical bonds but on weaker Coulomb, van der Waals or n-n interactions to connect CNTs to surface-active molecules such as surfactants, aromatics, biomolecules (e.g. DNA), polyelectrolytes and polymers. In most cases, this approach is used to improve the dispersion properties of CNTs [116], for example via charge repulsion between micelles of sodium dodecylsulfate [65] adsorbed on the CNT surface or a large solvation shell formed by neutral molecule (e.g. polyvinylpyrrolidone) [117] around the CNTs. 

Incremental Approach to Noncovalent Interactions Coulomb and van der Waals Effects in Organic Ion Pairs. 

---