Synthesis and properties of amphiphilic “dumbbell”-shaped grafted block copolymers, 1. Anionic synthesis via a polyfunctional initiator

Two poly(ethylene oxide) stars linked by a long polystyrene chain represent a novel amphiphilic architecture (dumbbell), which is available by anionic grafting of ethylene oxide from a hydroxylated polybutadiene-block-polystyrene-block-polybutadiene triblock copolymer. The short butadiene end-blocks (DPB = 36) of a BSB triblock copolymer with a long styrene middle block (DPS = 650) was first modified by hydroboration and oxidation. A multifunctional alkoxide initiator is thus prepared by titration of the hydroxyl groups of the “polybutadiene” end-block with cumylpotassium. Gelation and precipitation of the polyfunctional initiator in THF could be avoided by complexing the cation (K+) with a…