SUPRAMOLECULAR FORMATION OF TRIBLOCK COPOLYMERS IN POLAR NONPOLAR-SOLVENTS

Triblock copolymers could form supramolecules in either polar or nonpolar solvents at appropriate concentration and temperature ranges or in the presence of additives. The association properties and the structure of supramolecules of PEO-PPO-PEO and PPO-PEO-PPO (PEO and PPO refer to poly(oxyethylene) and poly(oxypropylene), respectively) triblock copolymers in xylene and/or water were investigated by using light scattering, small-angle neutron scattering, and small-angle X-ray scattering. The association process of aqueous solution or water-rich ternary systems was entropy driven and temperature played an important role. The additive, e.g., water in the oil-rich ternary system, played a very important role on the micellization of PEO-PPO-PEO, e.g., Pluronic L64, in xylene. The micelles had a core-shell structure and the micellar shell was rather heavily solvated. At high copolymer concentrations, large aggregates with a lamellar structure was formed and the amount of large aggregates increased with increasing copolymer concentration before gel formation.