Effect of binary block-selective solvents on self-assembly of ABA triblock copolymer in dilute solution

We have studied the self-assembly of the ABA triblock copolymer (P4VP-b-PS-b-P4VP) in dilute solution by using binary block-selective solvents, that is, water and methanol. The triblock copolymer was first dissolved in dioxane to form a homogeneous solution. Subsequently, a given volume of selective solvent was added slowly to the solution to induce self-assembly of the copolymer. It was found that the copolymer (P4VP(43)-b-PS366-b-P4VP(43)) tended to form spherical aggregate or bilayer structure when we used methanol or water as the single selective solvent, respectively.