Bilayer Morphologies of Self-Assembled Crew-Cut Aggregates of Amphiphilic PS-b-PEO Diblock Copolymers in Solution

Abstract

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 a...