Macromolecules, Vol.32, No.25, 8356-8362, 1999
High-yield synthesis of functionalized alkoxyamine initiators and approach to well-controlled block copolymers using them
Reaction of ethylbenzene, 4-bromo-, 4-(ethoxycarbonyl)-, and 4-methoxyethylbenzenes with di-tert-butyl diperoxyoxalate at 35 degrees C in the presence of stable nitroxide radicals gave alkoxyamines in 50-91% yields. Lithiation of the 4-bromophenylalkoxyamine and subsequent treatment with DMF gave 4-formylphenylalkoxyamine in 95% yield, and the reduction of the 4-formylphenylalkoxyamine with NaBH4 yielded 4-(hydroxymethyl)phenylalkoxyamine in 89% yield. Anionic polymerization of butadiene (BD) with sec-BuLi and subsequent termination with 4-formylphenylalkoxyamine gave an end-functionalized poly(butadiene) [poly(BD)]. "Living" radical polymerization of styrene (St) initiated by the functionalized poly(BD) at 120 degrees C gave a poly(BD)-block-poly(St) with a M-w/M-n of 1.30. Anionic polymerization of hexamethylcyclotrisiloxane (D-3) with 4-lithiophenylalkoxyamine gave poly(D-3) with an alkoxyamine moiety at a polymer end. "Living" radical polymerization of St initiated by the functionalized poly(D-3) gave poly(D-3)-block-poly(St) with M-w/M-n's of 1.73-1.80.
Keywords:FREE-RADICAL POLYMERIZATION;STYRENE POLYMERIZATION;EFFICIENTSYNTHESIS;NITROXIDE;POLYBUTADIENE;VERSATILE;REAGENTS;TEMPO