Mixing Terms Links

The q = 1 terms link the fine structure states the importance of this mixing is maximised when the separation between the fine-structure states is small (i.e. small spin-orbit splitting), and when the rotational constant B is large. Consequently molecules like CIO, BrO and 10 are good case (a)2 n systems, whereas CH obeys case (b) coupling, even in its lowest rotational levels. The OH radical approximates more closely to case (a) in its lowest rotational levels, but goes over to case (b) as the rotational quantum number increases. As we mentioned above, the transition from case (a) to case (b) is discussed in detail in chapter 9 it is not, of course, confined to 2n molecules. 

The condition of swelling equilibrium can be calculated by means of two theoretical approaches. It is assumed that the chemical potential of mixing for a network is the same as the chemical potential of mixing an uncross-linked polymer of high molecular weight and of the same structure as the network polymer. The mixing term can be described by means of the Flory-Huggins (FH) equation. The calculation of the elastic deformation term is based on the rubber elasticity theory (RET). 

The q = terms link the fine structure states the importance of this mixing is... 

The structure of hydrogels that do not contain ionic moieties can be analyzed by the Flory Rehner theory (Flory and Rehner 1943a). This combination of thermodynamic and elasticity theories states that a cross-linked polymer gel which is immersed in a fluid and allowed to reach equilibrium with its surroundings is subject only to two opposing forces, the thermodynamic force of mixing and the retractive force of the polymer chains. At equilibrium, these two forces are equal. Equation (1) describes the physical situation in terms of the Gibbs free energy. 

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