A RECORD 9 DIFFERENT PHASES (4 CUBIC, 2 HEXAGONAL, AND ONE LAMELLAR LYOTROPIC LIQUID-CRYSTALLINE AND 2 MICELLAR SOLUTIONS) IN A TERNARY ISOTHERMAL SYSTEM OF AN AMPHIPHILIC BLOCK-COPOLYMER AND SELECTIVE SOLVENTS (WATER AND OIL)

We report on a ternary isothermal system consisting of a poly(ethylene oxide)/poly(propylene oxide) (PEO/PPO) amphiphilic block copolymer, ' 'water'', and ''oil'' (where ''water'' and ''oil'' are selective solve nts for the different blocks), which exhibits the richest structural p olymorphism ever observed (in equilibrium) in mixtures containing amph iphiles (such as block copolymers, surfactants, or lipids). The micros tructure resulting from the self-assembly of the PEO/PPO block copolym er can vary from normal (oil-in-water) micelles in solution, through a ll types of normal and reverse (water-in-oil) lyotropic liquid crystal s (normal micellar cubic, normal hexagonal, normal bicontinuous cubic, lamellar, reverse bicontinuous cubic, reverse hexagonal, reverse mice llar cubic), to reverse micelles, as the relative volume fraction of t he apolar (''oil''-like) components increases over that of the polar ( ''water''-like) components. The structure in the liquid crystalline ph ases has been established with small-angle X-ray scattering; both the normal and the reverse bicontinuous cubic structures are consistent wi th the Ia3d crystallographic space group (and the Gyroid minimal surfa ce), while the normal and reverse micellar cubic structures are consis tent with the Im3m and FdSm space groups, respectively. The self-assem bly of amphiphilic block copolymer in selective solvents described her e provides a link between the self-assembly of surfactants in water (a nd oil/cosurfactant) and the self-assembly of block copolymers in the absence of any solvent. Furthermore, the ability of the PEO/PPO amphip hilic block copolymers to attain diverse microstructures is of great i mportance to numerous practical applications, especially since such co polymers are commercially available (as poloxamers, Pluronics, or Synp eronics).