Kinetic state diagrams for a highly asymmetric block copolymer assembled in solution.

ABSTRACT

Polymer self-assembly is used to form nanomaterials with a wide range of structures. While self-assembly of polymers in bulk has been thoroughly explored, the same process in solution remains widely used but partially unresolved, due to the formation of structures which are often kinetically trapped. In this paper we report kinetic state diagrams of polystyrene-b-poly(ethylene oxide) block copolymer in water by changing the solvent-switch assembly conditions. We study 36 different conditions for a single block copolymer, exploring three parameters polymer concentration, temperature and rate addition of selective solvent. The data shows that polymer concentration plays an important role in determining which morphologies are accessible within a given set of experimental parameters and provides evidence that vesicles can evolve into particles with complex internal structures, supportive of recent mechanistic studies. Most importantly, the data shows a complex relationship between all parameters and the resulting kinetically trapped morphologies indicating that combined in situ and ex situ studies are required to gain a fundamental understanding of kinetically controlled block copolymer assembly processes.