Phase Diagram of Systems: Block Copolymer-Preferential Solvent of One Block

Abstract

We have studied by small angle X-ray scattering and differential scanning calorimeter different systems block copolymer/preferential solvent of one block. For copolymers owning two amorphous blocks such as polystyrene-polybutadiene, in solution in toluene, we have only one liquid-crystalline structure which disappears at about 180°C; this structure is lamellar if the copolymer contains between 35 and 60% of polybutadiene. For copolymers owning an amorphous and a crystallizable block such as polystyrene-polyethyleneoxide, we have found two liquid-crystalline structures L.C. and L.L., which are both lamellar but differ by the state of the polyethyleneoxide chains. Below about 50°C we have found the structure L.C. with crystallized polyethyleneoxide chains; between 50 and about 170 °C, we have found the structure L.L. with liquid polyethyleneoxide chains. The field of the structure L.C. is smaller with nitromethane which is a preferential solvent of polyethyleneoxide than with diethylphtalate which is a preferential solvent of polystyrene.