Synthesis of novel asymmetric dendritic-linear-dendritic block copolymers via “living” anionic polymerization of ethylene oxide initiated by dendritic macroinitiators (original) (raw)

Abstract

The first synthesis of asymmetric dendritic-linear-dendritic ABC block copolymers, that contain a linear B block and dissimilar A and C dendritic fragments is reported. Third generation poly(benzyl ether) monodendrons having benzyl alcohol moiety at their ''focal'' point were activated by quantitative titration with organometallic anions and the resulting alkoxides were used as initiators in the ''living'' ringopening polymerization of ethylene oxide. The reaction proceeded in controlled fashion at 40-50 8C affording linear-dendritic AB block copolymers with predictable molecular weights (M w ¼ 6000-13,000) and narrow molecular weight distributions (M w /M n ¼ 1.02-1.04). The propagation process was monitored by size-exclusion chromatography with multiple detection. The resulting ''living'' copolymers were terminated by reaction either with HCl/tetrahydrofuran or with a reactive monodendron that differed from the initiating dendron not only in size, but also in chemical composition. The asymmetric triblock copolymers follow a peculiar structure-induced selfassembly pattern in block-selective solvents as evidenced by size-exclusion chromatography in combination with multi-angle light scattering.

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