KINETIC-STUDY ON THE CAPPING REACTION OF LIVING POLYISOBUTYLENE WITH 1,1-DIPHENYLETHYLENE - 1 - EFFECT OF TEMPERATURE AND COMPARISON TO THEMODEL-COMPOUND 2-CHLORO-2,4,4-TRIMETHYLPENTANE

The addition reaction of 1,1-diphenylethylene to polymeric and dimeric isobutylene living chain ends in the presence of TiCl4 was investigat ed in hexane/MeCl 60/40 (v/v) at -80 to -40 degrees C using on-line W- vis spectroscopy. The apparent equilibrium constants of capping/decapp ing, K-e, and the apparent rate constants of capping, k(c)K(i), were d irectly measured, and from these values, the corresponding rate consta nts of decapping, k(d), were calculated. The activation energy is foun d to be apparently negative for the capping reaction (k(c)K(i)) and po sitive for the decapping reaction (ha). However, the respective activa tion parameters for the polyisobutylene differ significantly from thos e of the dimer; i.e., the chain length affects the kinetics of the cap ping/decapping reaction.