Structures of ''crew-cut'' aggregates of polystyrene-b-poly(acrylic acid) diblock copolymers

''Crew-cut'' aggregates of polystyrene-b-poly(acrylic acid) block copolymers can be prepared by dissolving the copolymers in N,N-dimethylformamide (DMF) and adding water to the solution to induce aggregation of the styrene segments of the copolymer chains. The aggregates are formed at near-equilibrium conditions, and their structures are subsequently frozen by isolating them into aqueous solution by dialysis. Aggregates of a number of different morphologies have been prepared. The morphologies, identified by transmission electron microscopy, consist of spheres, rods, vesicles, lamellae, large compound vesicles, large compound micelles, etc. The formation of aggregates of different morphologies can be controlled by varying the copolymer composition, by changing the initial copolymer concentration in DMF, by adding ions (e.g. NaCl, CaCl2, HCl and NaOH, etc), or by adding homopolystyrene.