Living coupling reaction in living cationic polymerization. 4. Synthesis of telechelic polyisobutylenes using bis-furanyl derivatives as coupling agents

The synthesis of telechelic polyisobutylenes (PIB) by coupling with 2,5-bis -(2-furyl-2-propyl)furan is described. Hydroxyl tele-chelic PIB with contro lled molecular weight was obtained by haloboration-initiation of isobutylen e (IB) with a BCl3/BBr3 mixture, followed by coupling of the living ends an d oxidation of the (CH3O)(2)B- end groups with H2O2 in alkaline tetrahydrof uran. Vinyl telechelic PIBs were prepared by coupling living PIB obtained u sing a novel vinyl functional initiator 5-chloro-3,3,5-trimethyl-1-hexene i n conjunction with TiCl4 in hexanes/CH3Cl (60/40, v/v) at -80 degreesC. Chl orosilyl telechelic PIBs were synthesized for the first time by employing c hlorosilyl Functional initiators (1-chloro-1-methyl)ethyl-3-(1-dichloro-met hylsilyl-methyl)ethylbenzene and 1-methyldichlorosilyl-3,3,5-trimethyl-5-ch loro-hexane in conjunction with TiCl4 in hexanes/CH3Cl (60/40, v/v) at -80 degreesC. After coupling, the dichlorosilyl groups were converted to dimeth oxysilyl groups upon quenching with methanol. The bis-dimethoxysilyl telech elic PIBs were crosslinked by moisture at room temperature in the presence of catalytic amounts of tin(II) 2-ethyl-hexanoate. Extraction of the crossl inked samples with hexanes resulted in negligible soluble content, indicati ng essentially quantitative crosslinking.