Interactions in Polar Liquids

In this case the interaction between neighbouring molecules is not only stronger but also orientation dependent. The mean statistical energy of dipole-dipole interactions 0dd also decreases with r 6, but depends on i2 (p dipole moment) according to 3  

As a consequence of such interaction there are some preferential mutual orientation disturbed by the thermic motion of the molecules. 

Ion-dipole interactions interact over longer distances. Their mean interaction energy 0id decreases with r-4 3)  

Ion-ion interactions are long-range interactions decreasing only with r 1 and their mean interaction energy 0M is given by3) 

The typical properties of water arise from the ability of the water molecule to participate in four hydrogen bonds due to its two protons and its two lone electron pairs (2s)2 (2pz)2 which act as proton acceptors. In the condensed state, the angle between the 2px and the 2py orbital of oxygen is enlarged by hydridisation to a mixture of s- and p-state to 109°. Because both of the free electron pairs are situated in a plane 

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This term, though not significant for most polymer films, accounts for the AB-type interactions in polar liquids (for example, for water it accounts for the hydrophobic repulsion with Sp >0, Ip 0.2-l nm). The entropic confinement effects in polymer films due to adsorption/grafting at the film-substrate interface is also taken into account by this term and for this case Ip Rg (radius of gyration of the polymer). 

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