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Ions, chaotropic/cosmotropic

Water structural effects of ions may be assessed by a variety of experimental methods as well as by computer simulations. These methods lead to the recognition that some ions enhance the native structure of the water whereas other ions destroy it, up to some distance in the water away from the ion. The former ions are called structure-makers, or cosmotropic, a term favoured in the biophysical literature, and the latter kind of ions are structure-breakers or chaotropic. Naturally, there are also ions that are borderline between these groups, neither structure-makers nor -breakers to a significant extent. [Pg.99]

It is furthermore concluded that whereas the anion Hofmeister series is generally well established, with only few reversals that can be explained ad-hoc, this is not the case regarding the cation Hofmeister series. There are in general no head cations established in a series such as (5.8), erroneously termed chaotropic, nor general tail cations , erroneously termed cosmotropic, but for each surface the hydrophilic and hydrophobic character or balance between these properties is responsible for the order of cations interacting directly with sites at the surface, in addition to the ion properties mentioned above, see Table 5.4 for the latter. [Pg.188]

The observed ion-specific effects were associated with the hydrophobicity of the ions and the ions affinity to the polyelectrolyte. Later, Khtzing et al. explained this effect by the difference between cosmotropic and chaotropic ions [37]. The influence of specific anions on certain properties of PEMs has been investigated extensively by Salomaki et al. [28-30]. The anions tested within this work followed the famous Hofmeister series and gave an increasing storage shear modulus with increasing ion size. The latter result is in contradiction to the increase in chain mobihty found later by Nazaran et al. [24]. [Pg.1634]

Recently, Liu et al. have broadened the field of ion-specific effects on polyelectrolyte multilayers by investigation of the deposition of PSS/ PDADMAC multilayers in mixed electrolyte solutions (PDADMAC poly(diallyldimethy-lammonium chloride)) [22]. It appeared that the effects of anions of a mixed electrolyte solution on the deposition of PEMs are nonadditive. Moreover, in a mixed electrolyte solution containing both chaotropic and cosmotropic anions, the multilayer buildup is dominated by chaotropic anions. [Pg.1634]

Nevertheless, the term cosmotropic only means that the if is energetically strongly hydrated and chaotropic that it is energetically weakly hydrated. Note that this classification is not in phase with Pearson s concept of hard and soft i(Mis. Ag and Hg " are soft ions, but their enthalpies of hydratiOTi —483 and — 1,853 kJ mol respectively are more negative than those of the hard irais of similar size, Na and with values... [Pg.2048]

Removal of the inconsistency in the manner Ninham, Bostrom and co-workers have described in a series of papers goes part of the way to a resolution, but only at the level of the primitive model. More is involved once the molecular nature of the solvent is taken into account. Ionic polarisability is combined at the same level with electrostatics to determine local induced water structure around ions. That is a key determinant of hydration, and of so-called ion specific Gurney potentials of interactions between ions due to the overlap of these solute-induced solvent profiles so too for ionic adsorption at interfaces. The notions involved here embrace quantitatively the conventional ideas of cosmotropic, chaotropic, hard and soft ions. Some insights into this matter can be obtained via the alternative approach of computer simulation techniques of Jungwirth etal. But the insights are hamstrung so far by a pragmatic restriction that limits... [Pg.296]


See other pages where Ions, chaotropic/cosmotropic is mentioned: [Pg.97]    [Pg.172]    [Pg.220]    [Pg.220]    [Pg.762]    [Pg.763]    [Pg.1131]    [Pg.1634]    [Pg.1635]    [Pg.2048]    [Pg.317]   
See also in sourсe #XX -- [ Pg.156 , Pg.163 , Pg.269 , Pg.270 , Pg.275 ]




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Chaotrope

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