SynopsisThe polymerization of isobutylene using +&l coinitiator and the tertiary chlorides tert.-butyl chloride (t-BuC1) and 2,6-dichloro-2,6-dimethylheptane (Clf-R-Clf) initiators has been studied. Polymerization rates with the t-BuCl/&Al and Clt-R-Clt/+3Al initiating systems were high in the -20 to -7OOC range. Yields and molecular weights increased with decreasing temperature. As predicted by model experiments the extent of phenylation increases with decreasing temperatures. According to spectroscopic evidence the polyisobutylenes carry phenyl end groups.* A preliminary report concerning this research has appeared

Synopsisa,w-Diphenylpolyisobutylenes produced by the Clt -R-Clt/&Al initiating system have been derivatized. Model chloromethylation of t-butylbenzene by CH30CH2Cl in chloroform indicated that beyond ca. 35% yield significant alkylative side reactions occurred. Phenyl end groups (average 1.5 per chain) and unsaturated chain ends (from proton elimination) have been converted to carboxyl end groups by oxidation with RuOd in chloroform. Subsequently the carboxyl end groups were converted to acyl chloride termini by reaction with SOC12. The latter end groups were coupled with living polystyryl anions t o form isobutylene-styrene block copolymers.The oxidized PIB was chlorinated by SOClz in n-heptane under a nitrogen atmosphere. After three washings with n-heptane, the sulfur content was less than 150 ppm [negative Ba(N03)~ + H20 test]. The GPC trace of the chlorinated PIB (M, = 12 X lo3) indicated that polymer degradation did not occur during chlorination (see Fig. 2). The chlorinated product was used for coupling with living polystyryl anions.

SynopsisPreparatory for the synthesis of terminally functional polyisobutylenes carrying one or two phenyl end groups, model experiments have been carried out using novel tert-butyl chloridehiphenylaluminum and 2,6-dichloro-2,6-dimethylheptane/triphenylaluminum initiating systems. As anticipated, t-BuC1 was phenylated by I#J3Al and the product is tert-butylbenzene. The reaction is extremely rapid and temperature has little effect on it in the 0 to -6OOC range. The interaction between the 2,6-dichloro-2,6-dimethylheptane and &A1 was found to be complicated by a proximity effect which leads to proton elimination in addition to phenylation. The formation of the desired diterminally phenylated product is not quantitative even at -60°C.

Model experiments and subsequent polymerization runs have been carried out to elucidate the mechanism of cationic olefin polymerizations initiated by aromatic carbenium ions. Thus, the p‐methylbenzylation of 2,4,4‐trimethyl‐1‐pentene, a nonpolymerizable model olefin for isobutylene, was investigated by using the p‐CH3C6H4CH2Cl/Et3Al initiating system and CH2Cl2 solvent under various conditions. All the important organic reaction products were identified and most of them, quantitatively determined. Analysis of the nature of the products and their distributions gave important mechanistic information about the chemistry of elementary events and their relative rates; for example, hydridation and ethylation by the Et3AlCl⊖ counteranion of various cations occurs and these processes mimic termination in carbocationic polymerizations. Hydridation and ethylation are much faster than proton elimination (chain transfer in polymerization) and experimental conditions (e.g., Al/Cl ratio and temperature) influence the relative rates of these processes. According to model experiments, the p‐CH3C6H4CH2Cl/Et3Al system may initiate olefin (isobutylene) polymerization; chain transfer to monomer should be relatively unimportant, but rapid hydridation or ethylation should reduce the kinetic chain and give low conversions. Predictions derived from model experiments were substantiated by polymerizations with isobutylene and the aromatic initiating system.