Nanostructured Aggregates From The Self-Assembly Of Bab Triblock Copolymers With A Hydrophilic Middle Block A In Water

Abstract

The self-assembled nanostructured aggregates with various morphologies, including spherical micelles, worm-like micelles, vesicles and lamellae, have benn observed from the BAB triblock copolymers in water. Here, the polymers used are Polystyrene(PS)43-b-Poly(ethylene oxide)(PEO)45-b-PS43 copolymer with Mw/Mn = 1.48 prepared by ATRP and PS39-b-Poly(4-vinylpyridine)(P4VP)98-b-PS39 copolymer with Mw/Mn = 1.15 synthesized by RAFT. The size and shape of the aggregates are controllable according to some tunable parameters of systems, which affect the balance between three of the major forces acting on the system. These include the stretching of the core-forming blocks, the intercoronal interactions, and the interfacial energy between the solvent and the micellar core. The multiple morphologies were obtained by altering the solvents, solvent composition, copolymers, pH, concentrations, and so on. In addition, the second aggregation behavior of spherical micelles, spherical vesicles, and worm-like micelles was interestedly concerned. It was found that the second aggregation behavior the different complexity for different primary aggregates. For symmetrical primary aggregates, such as spherical micelles and vesicles, the second aggregates appeared symmetrically spherical. In contrast, for unsymmetrical worm-like primary micelles, the second aggregation tended to have unsymmetrical shape. The BAB chain architecture was molecularly suggested to be responsible for the second aggregation.