Cationic polymerizations by aromatic initiating systems. V. Oxidation and chlorination of α,ω‐diphenylpolyisobutylene and subsequent reaction with living polystyrene anions to form block copolymers

Abstract

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.

End-Quenching of TiCl4-Catalyzed Quasiliving Polyisobutylene with Alkoxybenzenes for Direct Chain End Functionalization

“…When Russell et al [51][52][53][54][55][56] conducted SnCl 4 -catalyzed isobutylene polymerizations in ethyl chloride at -78.5 °C with phenol and substituted phenols as cocatalysts (initiators), they found evidence of phenolic end groups; however, proton expulsion was also a significant chain breaking event, leading to terminal unsaturation. 57 The first attempts at controlled termination of carbocationic polymerizations with an arene were reported by Kennedy et al [58][59][60][61] when they used a triphenylaluminum/tert-alkyl chloride initiating system. The arylaluminum acted as both a catalyst and chain terminating agent, yielding R,ω-diphenyl PIBs with 0.7-1.7 phenyl groups per chain.…”

“…The first attempts at controlled termination of carbocationic polymerizations with an arene were reported by Kennedy et al − when they used a triphenylaluminum/ tert -alkyl chloride initiating system. The arylaluminum acted as both a catalyst and chain terminating agent, yielding α,ω-diphenyl PIBs with 0.7−1.7 phenyl groups per chain.…”