Electric Field Induced Gyroid-to-Cylinder Transitions in Concentrated Diblock Copolymer Solutions

Block copolymers show a variety of microdomain structures due to their ability to phase separate. The bicontinuous gyroid phase and its behavior under the influence of external fields are particularly interesting with regard to technological applications. In this paper, we studied the behavior of a gyroid-forming block copolymer solution under the influence of an external electric field. As a model system, we used a solution of polystyrene-b-polyisoprene in toluene. We will show that the gyroid phase can be aligned by a moderate electric field and can be forced to undergo a phase transition to the cylindrical phase under a sufficiently high electric field. This process is reversible, and the cylinders immediately reconnect after the electric field is switched off, generating a highly aligned gyroid phase.