Phase Behavior of Vesicle‐Forming Block Copolymers in Aqueous Solutions

The binary phase diagram of amphiphilic poly(ethylene oxide)‐ block ‐poly( γ ‐methyl‐ ε ‐caprolactone) block copolymers in water is examined for four polymers having the same hydrophilic block length but different hydrophobic block lengths across the whole concentration range. The bulk polymers show no ordered morphology. With increasing water concentration the polymers undergo transitions from lamellar phases to packed vesicles and subsequently all polymers self‐assemble into vesicles in dilute aqueous solutions. Additionally, the largest polymer forms an inverse hexagonal phase, and the smallest polymer self‐aggregates into rod‐like micelles and showed a hexagonal phase.