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

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