Hydrophobicity at different length scales

There is, however, no strong inducement for a small number of small hydrophobic groups to associate in water. It is more likely that water can separate such species rather than drive them together. Small-length-scale hydrophobic interaction can be understood in terms of Stillinger s scaled particle theory and the integral equation theory of Pratt and Chandler. Of course, association/coagulation of non-polar solutes occurs when concentration of the solute is increased beyond a critical concentration. The critical micellar concentration is an example of such an association. 

The hydrophobic effect is important in both biology and chemistry and is a clear manifestation of the extensive HB network present in water. At room temperature this effect is essentially entropic in origin. However, the enthalpic stabilizing 

However, the hydrophobic force between two non-polar moleeules, often termed pair hydrophobieity, is yet to be fully understood. Also, the origin of an unusually strong hydrophobie force between two hydrophobie surfaees (with water in between), at distanees 100-150 A apart, has not been explained. 

In the next ehapter we diseuss the water stmeture and dynamies around amphi-philie moleeules, where one part of the moleeule attraets while another repels. 

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