Shift of equilibria between ions, ion pairs, and esters

1 SHIFT OF EQUILIBRIA BETWEEN IONS, ION PAIRS, AND ESTERS 

Equilibria between various forms of living centres were treated in Chap. 5, Sect. 8.1. Equilibria of similar character control the arrangement and reactivity of all ionic centres. When polymerization-inactive structures participate in the equilibria, the number of active centres is reduced by the equilibrium amount of inactive forms. This phenomenon is usually not considered as termination the unreactive particles are treated as dormant. In the course of polymerization, however, the physico-chemical parameters of the system change as a function of the monomer-polymer transformation. Changes in permittivity, viscosity and the amount of polymer can cause shifts in ionization and dissociation equilibria. The kinetic manifestations of such changes are identical with the occurrence of termination. 

These phenomena have not been studied quantitatively. The interest of most authors studying dissociation equilibria is limited to polymerizations 

Ionic equilibria can be shifted by the addition of salts containing a common ion with the active centre. These shifts have been treated in Chap. 5, Sect. 8.1 they cannot, of course, be designated as termination even though they are accompanied by a considerable lowering of the polymerization rate. 

An addition of a suitable electrolyte to an ionically polymerizing system can, however, lead to almost instantaneous and quantitative termination of centres when the ionic equilibria are shifted completely towards the inactive species. Saegusa and Matsumoto stopped the polymerization of tetrahyd-rofuran by sodium phenolate [90] 

---