Solvent vapor induced structural evolution of micelle clusters and square slices that form in PS-b-PEO solutions

Micelle clusters and square slices that formed in different polystyrene-b-poly(ethylene oxide) (PS-b-PEO) solutions were observed with AFM. This diblock copolymer assembled into small spherical micelles and then micelle clusters (diameters: 100–400 nm) after the PS-b-PEO/toluene solution had been aged for 24 h at room temperature. Square slices were obtained from solutions aged for two months. Solvent vapor induced morphological and structural transitions of the micelle clusters and the stability of the square slices on Si wafers were investigated. The results showed that the solvent vapor induced morphology of the sample aged for 24 h was more ordered than that aged for two months. Possible mechanisms for the formation of these structures in the solutions and the vapor-induced structural transition were proposed.