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.