Disk morphology and disk-to-cylinder tunability of poly(acrylic acid)-b-poly(methyl acrylate)-b-polystyrene triblock copolymer solution-state assemblies.

Disk and cylindrical micellar assemblies were formed through self-organization of poly(acrylic acid)-b-poly(methyl acrylate)-b-polystyrene (PAA-b-PMA-b-PS) amphiphilic triblock copolymers with organic diamines as counterions in water/ tetrahydrofuran (THF) solvent mixtures. The system was investigated by means of transmission electron microscopy and cryogenic transmission electron microscopy. It was found that the assembled-state morphologies could be modified by alteration of the type and concentration of cationic diamine counterion undergoing interaction with the negatively charged, polyelectrolyte PAA corona block, the relative amount of water in the water/THF mixture, and the hydrophobic block chain length. Multivalency of the organic amine counterion was critical for disk formation. It was further demonstrated that a single block copolymer underwent disc-to-cylindrical micellar transitions reversibly with variation in the relative water/THF ratio. The ability to form disks beginning from either THF-r...