Tunable phase behaviors of diblock copolyelectrolytes under alternating electric fields: A coarse-grained molecular dynamics study

Diblock copolyelectrolytes have significant potential in applications such as solid-state single-ion conductors, but precisely controlling their nanostructures for efficient ion transport remains a challenge. In this study, we explore the phase behavior and microphase transitions of AX BY-type diblock copolyelectrolytes under alternating electric fields using coarse-grained molecular dynamics simulations. We systematically investigate the effects of various electric field features, including unipolar and bipolar square-waves, as well as offset and non-offset sine-waves, focusing on how field strength and period influence the self-assembling morphology of the copolyelectrolytes. Under unipolar square-waves, both the lamellar and cylindrical phase regions expand, while the disordered phase regions shrink as the field strength increases. In contrast, bipolar square-waves maintain lamellar structures more robustly, with reversed stretching behavior observed in the polymer chains. As the electric field period exceeds a critical value, both waveforms converge with the results seen under constant electric fields. In addition, sine-waves induce smoother phase transitions, expanding the ordered phase regions, particularly the cylindrical phase, due to continuous field variation. We further examine the detailed structural and dynamic properties, such as mean-square displacement, polymer conformation, and chain orientation during these transitions. This work provides fundamental insights into the structural regulation of diblock copolyelectrolytes under oscillating electric fields, guiding the design of advanced polymeric electrolytes with tailored nanostructures.