Self-assembly of block copolymers in selective solvents: influence of relative block size on phase behavior

Two isothermal (25°C) phase diagrams with the block copolymer (EO)₄₃(PO)₁₆(EO)₄₃ and the block copolymer (EO)₅(PO)₆₈(EO)₅, respectively, in water and p-xylene are presented (EO is ethylene oxide and PO is propylene oxide). The copolymers have approximately the same molecular weight, albeit are unbalanced in PEO/PPO block ratio. The amounts and relative proportions of the solvents can modulate the resulting microstructures, although the phase sequence observed depends on the relative PEO/PPO block ratio. The copolymer rich in EO forms predominantly normal (oil-in-water) structures while the copolymer rich in PO forms predominantly reverse (water-in-oil) structures.