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 repr esent a novel amphiphilic architecture (dumbbell), which is available by anionic grafting of ethylene oxide from a hydroxylated olybutadiene -block-polystyrene-block-polybutadiene triblock copolymer. The short b utadiene end-blocks (DP(B)BAR = 36) of a BSB triblock copolymer with a long styrene middle block (DP(S)BAR = 650) was first modified by hydr oboration 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 polyf unctional initiator in THF could be avoided by complexing the cation ( K+) with a suitable cryptand (Kryptofix[2.2.2](TM)). This multifunctio nal macroinitiator was used to polymerize ethylene oxide. Dumbbell-sha ped molecules with various number and length of PEO branches were synt hesized. Some first results about their solution properties are presen ted and discussed based on viscosity and light scattering measurements .