BLOCKING-GROUP INITIATORS FOR THE SYNTHESIS OF POLYROTAXANES VIA FREE-RADICAL POLYMERIZATIONS/

Two new blocking group/initiators (BG/inits) were prepared. 4,4'-Azobi s[4-cyanopentanoic acid] (7) was converted to 4,4'-azobis[4-cyanopenta noyl chloride] (8). The acid chloride 8 reacted with 4,4-bis(p-tert-bu tylphenyl)-4-phenylbuta (5) to give 4,4-bis(p-tert-butylphenyl)-4-phen ylbuty 4,4'-azobis[4-cyanopentanoate] (9, BG/init I) in quantitative y ield. 4-[Tris(p-tert-butylphenyl)methyl]phenyl 4,4'-azobis[4-cyanopent anoate] (10, BG/init II) was synthesized by room temperature esterific ation of 4,4'-azobis[4-cyanopentanoic acid] (7) with tris(p-tert-butyl phenyl)(4-hydroxyphenyl)methane (6) using the DCC coupling method. The results of the polymerization of styrene initiated by I and II indica ted that both the BG/inits were well-behaved free radical initiators. Also, terminal group analysis by 1K NMR spectra showed that the blocki ng efficiencies for polystyrene were 100% due to the termination via r adical coupling. These BG/inits can be used as free radical initiators and blocking groups at the same time in the synthesis of polyrotaxane s prepared by radical polymerizations.