SUPRAMOLECULAR FORMATION OF TRIBLOCK COPOLYMERS IN POLAR NONPOLAR-SOLVENTS

Triblock copolymers could form supramolecules in either polar or nonpo lar solvents at appropriate concentration and temperature ranges or in the presence of additives. The association properties and the structu re of supramolecules of PEO-PPO-PEO and PPO-PEO-PPO (PEO and PPO refer to poly(oxyethylene) and poly(oxypropylene), respectively) triblock c opolymers in xylene and/or water were investigated by using light scat tering, small-angle neutron scattering, and small-angle X-ray scatteri ng. The association process of aqueous solution or water-rich ternary systems was entropy driven and temperature played an important role. T he 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 L6 4, 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 o f large aggregates increased with increasing copolymer concentration b efore gel formation.