Vesicles formed from a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in dilute aqueous solution

Hydrophobic polyethylene oxide-polypropylene oxide-polyethyelene oxide (PEO-PPO-PEO) triblock copolymers in dilute water solutions was prepared to form a vesicles by extrusion method. The triblock copolymer vesicle consists of a polymer layer, with a PPO interior shielded by PEO layers on each side that encloses a water compartment. The time stability of L121 vesicles was investigated by turbidity measurements. The turbidity increases by approximately 50% within the chosen time interval which shows that these vesicles are not thermodynamically stable. After sufficiently long time, the vesicle solution eventually reverts to its original state as a dispersed lamellar phase in equilibrium with an Lα phase.