The addition of ions in micromolar (CaCl2 or HCl) or millimolar (NaCl) concentrations can change the morphology of "crew-cut" aggregates of amphiphilic block copolymers in dilute solutions. In addition to spherical, rodlike, and univesicular or lamellar aggregates, an unusual large compound vesicle morphology can be obtained from a single block copolymer. Some features of the spontaneously formed large compound vesicles may make them especially useful as vehicles for delivering drugs and as models of biological cells. Gelation of a dilute spherical micelle solution can also be induced by ions as the result of the formation of a cross-linked "pearl necklace" morphology.

Block ionomer complexes formed between the block copolymers containing poly(sodium methacrylate) (PMANa) and poly(ethylene oxide) (PEO) segments and poly(N-ethyl-4-vinylpyridinium bromide) (PEVP) were investigated. The data obtained suggest that (i) these systems form water-soluble stoichiometric complexes; (ii) these complexes are stable in a much broader pH range compared to the polyelectrolyte complexes prepared from homopolymers; (iii) they self-assemble to form the core of a micelle comprised of neutralized polyions, surrounded by the PEO corona; (iv) they are salt sensitive since they fall apart as the salt concentration increases beyond a critical value; and (v) they can participate in the cooperative polyion substitution reactions. Therefore, these complexes represent a new class of hybrid materials which combine properties of polyelectrolyte complexes and block copolymer micelles.

A wide range of bilayer aggregates, among them tubules, vesicles, large compound vesicles (LCVs), and lamellae, were prepared from various polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymers, and studied by transmission electron microscopy (TEM). The preparation method involved copolymer dissolution in DMF at room temperature, followed by the addition of water. In addition, it was found that aggregates of various morphologies can be prepared from an identical block copolymer by changing the solvent from DMF to a water−DMF mixture, by the addition of electrolytes, or by the use of subambient temperatures. All of these methods can be used to facilitate the formation of specific bilayer aggregates. When the preparation method involved copolymer dissolution in water−DMF mixtures, it was found that the morphologies of aggregates under certain conditions also depended on the annealing time. For example, the ratio of tubules to vesicles is related to the annealing time; only tubules appear at long annealing times, while vesicles and tubules coexist at short annealing times. Possible mechanisms for the formation of the bilayers are discussed. Tubules with oscillatory perturbations in their diameters are seen; these might be intermediates in the vesicle to tubule transition. Lamellae are observed frequently in the present system. In addition, bent lamellae have been observed for the first time; they may be intermediates in the lamella to vesicle transition, as suggested by some theories dealing with small molecule amphiphiles. The present system is believed to be the first to yield stable block copolymer amphiphile tubules, as well more complex tubular or vesicular aggregates, such as “plumber's nightmare”, starfishlike vesicles, budding vesicles (i.e. a chain of vesicles), and vesicles consisting of one or more small internalized vesicles within a larger one. Some of the morphologies are biomimetic.