M. Givehchi et al., Influence of 2,6-di-tert-butyl-4-methylpyridine on the polymerization of indene initiated with cumyl chloride/tin tetrachloride, MACROMOLEC, 33(26), 2000, pp. 9512-9517
The controlled polymerization of indene initiated with cumyl chloride and t
in tetrachloride in methylene dichloride solution shows first-order kinetic
s with respect to SnCl4, which implies the existence of simple equilibria f
or ionization and dissociation, contrary to the case of TiCl4. Experiments
in the presence of a hindered base (2,6-di-tert-butyl-4-methylpyridine) all
owed to estimate the propagation rate constant for paired and unpaired ions
in the range of 5 x 10(4)-10(5) L mol(-1) s(-1) at -40 degreesC. A fast in
itial polymerization, which takes place in the absence of base, and is supp
ressed by the base, is attributed to the larger dissociation constant for t
he Cum(+),SnCl5- ion pairs than for the polyindenyl ones, yielding a transi
tory excess of free ions. The hindered base suppresses the formation of fre
e ions, may act as a proton trap in the case of zero order transfer, and ma
y also be involved in bimolecular termination.