NEW POLYISOBUTYLENE STARS - XI - SYNTHESIS AND CHARACTERIZATION OF ALLYL-TELECHELIC OCTA-ARM POLYISOBUTYLENE STARS

The synthesis and characterization of a novel star comprising eight al lyl-terminated polyisobutylene (PIB) arms radiating from a calix[8]are ne core is described. The synthesis was accomplished by a core-first m ethod, by inducing the living polymerization of isobutylene (IB) by a suitably functionalized calix[8]arene initiator (1) conjunction with B Cl3-TiCl4 coinitiators, and terminating the growth of the living PIBarms by allyltrimethylsilane. The relative concentrations of BCl3, and TiCl4, are critical for the synthesis of well-defined 8-arm stars. Ch aracterization of the products (which included triple detector GPC stu dies and H-1 NMR spectroscopy) indicated quantitative allylation. A me chanism which summarizes the experimental observations is proposed.