Hydrophobic hydration, enthalpic effect

Table III. Values of the Enthalpic Effect of Hydrophobic Hydration Hb(H20), the Number of Water Molecules per Alkyl Group N/4 Correlated with It, and the Mean Deviations of the Calculated from...

In this equation R4N+. . . (H20)n denotes the resulting hydrophobic entity and K is an equilibrium constant. The enthalpic effect of hydro-phobic hydration then can be considered as the result of the formation of this hydration complex. In both models the choice of the cosolvent ought to be rather unimportant as long as this solvent does not show specific interactions like hydrogen bonding. As a consequence n and HbW should not vary with the different cosolvents. Besides that, the basic assumption in the concepts is that in the absence of hydrophobic hydration AH° would change proportionally to the solvent composition. In this chapter we will investigate more systematically both aspects. 

Poly(diallyldimethylammonium chloride) (PDADMAC) and ferri-/ferrocyanide show a similar behavior [233]. In most cases, the ferri-/ferrocyanide (trivalent/ tetravalent hexacyanoferrate[lll]/[ll]) couple exhibits an unexpected interaction pattern with strong cationic polyelectrolytes. Hereby, the trivalent ferricyanide favors complexation compared with the tetravalent ferrocyanide [234, 235]. Although the higher charged ferrocyanide is supposed to release a higher number of monovalent counterions, this entropic contribution is less dominant for the ferrocyanide. This conclusion was derived from entropy measurements [232], clearly emphasizing the enthalpic repulsion between the highly hydrated, weakly polarizable ferrocyanide and the somewhat hydrophobic polymeric backbone [236]. This leads to pronounced ion-specific effects. In contrast, some systems... 

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