Control of Diblock Copolyelectrolyte Morphology through Electric Field Application

Diblock copolyelectrolytes have received extensive attention in recent years due to their wide applications as novel solid-state and polymeric electrolytes; however, predictably tuning the morphologies and microphase structures of the diblock copolyelectrolytes for their performance optimization remains a significant challenge. In this paper, using coarse-grained molecular dynamics simulations, we discover a cascade of microphase structures of the AXBY-type diblock copolyelectrolytes (composed of a hydrophobic block AX and a polyelectrolyte block BY) through the application of an external electric field. Importantly, we find that the percolated phases of charged blocks which are desired for ion transportation can be realized at different block ratios solely through electric field regulations. Specifically, our simulations show that with increasing the electric field strength, (i) copolyelectrolytes at the block ratio of fA = X/(X + Y) = 0.67 undergo the lamellar–cylindrical–disordered microphase transitions; (ii) copolyelectrolytes with fA = 0.50 undergo cylindrical–disordered microphase transition; and (iii) copolyelectrolytes at fA = 0.33 experience the spherical–cylindrical–disordered transitions. The newly formed microphases caused by the electric field application can stably exist as the electric field is switched off and further re-enter the initial microphases through appropriate annealing manipulations. In particular, we systematically investigate the formation mechanisms and structural properties for each microphase and summarize the dependence of diverse morphologies of diblock copolyelectrolytes on the electric field strengths and directions, block ratios, and system temperatures. Our work contributes to the fundamental understanding of charged block copolymers in response to external electric fields and provides insight into the design and development of novel polymeric electrolytes with predesigned structural/thermodynamic properties.