INCREASE OF THE AVERAGE REACTIVITY OF ACTIVE SPECIES DUE TO A SHIFT TO THE MORE REACTIVE SPECIES IN IONIC PROPAGATION ACCOMPANIED BY TERMINATION

The presented simulations demonstrate that in polymerizations proceedi ng on two kinds of species, differing in reactivity and being in equil ibrium, the expected decrease of the rate of polymerization due to ter mination may happen to be compensated by the relative increase of conc entration of the more reactive species. This takes place, for instance , in the polymerization proceeding simultaneously on ions and ion pair s if ions are more reactive. Because of termination the total concentr ation of ionic species during the course of polymerization decreases w hile the proportion of ions increases due to increasing dilution. The maximum compensation is observed when simultaneously k(ions)/k(ion) pa irs) --> infinity and K(d)/[I]0 --> 0, where k are the propagation rat e constants, K(d) is the equilibrium constant of dissociation and [I]0 is the starting concentration of initiator. Then, the degree of compe nsation (the ratio of the rate with compensation to the rate without t ermination) is becoming equal to ([P]/[P*]0)1/2, where [P*] is the ac tual, total concentration of the growing species and [P]0 is the init ial total concentration (before any termination has taken place).