Single-solvent preparation of crew-cut aggregates of various morphologies from an amphiphilic diblock copolymer

Crew-cut aggregates of different morphologies, prepared from polystyrene-b- poly(acrylic acid) (PS-b-PAA) (with long PS blocks and short PAA blocks), w ere obtained through a single-solvent method. Low alkanols (i.e., methanol to n-butanol) were used as solvents. The hydrophobic block is solubilized a t elevated temperatures, and on cooling, the decrease in temperature induce s self-assembly. The short PAA block remains soluble throughout. Since the low alkanols have relatively low boiling points, confinement under pressure is required. However, it is the elevated temperature, rather than the pres sure, which is responsible for the success of the method. Parameters such a s the temperature, the copolymer concentration, and the nature of the solve nt have a morphogenic effect, leading to the formation of aggregates with a range of morphologies.