SYNTHESIS OF ISOBUTENYL-TELECHELIC POLYISOBUTYLENE BY FUNCTIONALIZATION WITH ISOBUTENYLTRIMETHYLSILANE

Isobutenyl-telechelic polyisobutylenes (PIBs) were synthesized by reac ting telt-chlorine-telechelic and living PIBs with isobutenyltrimethyl silane (IBTMS) in the presence of TiCl4 in CH2Cl2/hexane (40/60 v/v) s olvent mixtures at -78 degrees C. In order to obtain PIE oligomers, li ving polymerization of isobutylene was induced by the di-(2-hydroxy-2- propyl)-5-tert-butylbenzene (tBuDiCumOH)/BCl3 combination in CH2Cl2 fo llowed by addition of required amounts of hexane and TiCl4 to avoid po lymer precipitation and permanent termination. Although quantitative e nd-quenching of living PIE was achieved with IBTMS, chain coupling bet ween the living PIE chains and isobutenyl-ended polymers also occurred . This side reaction was avoided by isobutenylation of tert-chlorine-t elechelic PIE with IBTMS in the presence of TiCl4. The resulting isobu tenyltelechelic PIE contains exclusively exo-CH2-C(CH3)=CH2 endgroups, and is free from -CH=C(CH3)(2) endo olefins usually obtained in small quantities (similar to 3-8% of total double bonds) as a side product of other methods used in the past. (C) 1997 Elsevier Science Ltd.