Macrocyclic extractants behavior

Usually the description of the phase transfer behavior is presented in a simplified form based on the overall extraction equilibrium. This is illustrated schematically for a simple ion-pair extraction of a metal ion by a neutral macrocyclic extractant in Fig. 4.4. 

Physico-chemical studies and extraction techniques were carried out on soluble polymeric crown ethers. The pioneering work in this field was made by Smid who prepared several polymers or copolymers based on vinylbenzocrown ether and reported extensive data on the complexation of alkali picrate salts in various solvents including water. These polymers exhibit a high complexation of alkali cation, a selectivity related to the dimension of the cavity size of the macrocycle, a cooperative binding of the macrocyclic moieties of the polymer and a polyelectrolyte behavior. 

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