The run number (RN), the average number of monomer units added per ionization−termination cycle, was measured at −70 °C from first-order kinetic data for cationic quasi-living polymerization of styrene and isobutylene initiated with 5-tert-butyl-1,3-bis(2-chloro-2-propyl)benzene (bDCC)/TiCl4 in 60/40 MCHex/MeCl, via analysis of an initiation event termed rapid monomer consumption (RMC). RMC is characterized by an initial period of high polymerization rate followed by slower first-order decay in monomer concentration and is due to a larger ionization rate for the initiator compared to that for the polymer chain end. Styrene RN was found to decrease with increasing initiator concentration while that for isobutylene remained relatively unchanged; the dependence of styrene RN on initiator concentration was attributed to chain transfer to initiator during RMC. RN in the limit of zero initiator concentration was determined to be 39 and 4.7 for 0.5 M styrene and isobutylene, respectively. Apparent rate constants of chain-end ionization, k i, of 1.3 and 15 M-2 s-1 and rate constants of ion-pair collapse of 1.9 × 107 and 7.5 × 107 s-1 for styrene and isobutylene, respectively, were calculated. The latter were calculated using a value for k p of 1.5 × 109 M-1 s-1 for styrene and 7 × 108 M-1 s-1 for IB; apparent rate constants of chain-end ionization were determined independently of k p, from k - i/k p and k app.

A novel method of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis of isobutylene homopolymers is reported in this paper. Because of the difficulty in attaching ions for such materials, the ionization for MALDI-TOF MS analysis is realized by sulfonating the olefin end groups to introduce a readily ionized moiety into the polymer. Polyisobutylene samples obtained from both living cationic polymerization and industral procedures are studied here. The number-average molecular weights and weight-average molecular weights of these materials were also measured by laser light scattering and vapor pressure osmometry. Results obtained from the three techniques agree closely with one another except for the fraction having the highest molecular weight. We postulate that this is due to the range of the molecular weight of this sample being too broad to be accurately measured by MALDI-TOF MS.