R. Storey, Kelly A. Shoemake
Oct 1, 1997
SummaryA series of multi-arm star-branched polyisobutylenes was synthesized via living carbocationic polymerization. Arms with molecular weights ranging from 10, 000 to 30, 000 g/mol were prepared using the cumyl chloride/TiCl4/pyridine initiation system in 60/40 (v/v) hexane/methyl chloride at −80°C and linked by sequential addition of divinylbenzene. The weight average number of arms per star polymer, −Nw, scaled inversely with arm molecular weight and ranged from 32 to 5. Star-telechelic ionomers were produced by sulfonation of the aromatic initiator residue at the end of each arm, followed by neutralization. Sulfonation was quantitative as indicated by acid-base titration. Potassium ionomers were elastic solids which were marginally soluble in THF; the precursors were tacky and freely soluble in THF. Ionic modification did not alter the glass transition temperature (−66°C), but the thermal decomposition temperature in N2 was increased from 375 to 400°C.