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), were obtained through a single-solvent method. Low alkanols (i.e., methanol to n-butanol) were used as solvents. The hydrophobic block is solubilized at elevated temperatures, and on cooling, the decrease in temperature induces 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 pressure, which is responsible for the success of the method. Parameters such as the temperature, the copolymer concentration, and the nature of the solvent have a morphogenic effect, leading to the formation of aggregates with a range of morphologies.