Electric field influenced alignment of symmetrical lamellar diblock copolymers confined within polar discs.

Controlling self-assembly by employing a surface field in diblock copolymer melts manipulates nanoscale morphologies with potential applications in optics, sensors, nanolithography templates, and high-density media. In this paper, control is achieved by predicting alignment behaviour using an electric field applied to symmetric diblock copolymer melts confined in annular discs. The investigation focuses on new orientations of lamellar patterning resulting from microphase separation, influenced by the strength of the electric field and by variations in pore size and the disc's internal radius. The cell dynamics simulation model is a discrete version of the time-dependent Ginzburg-Landau (Cahn-Hilliard-Cook) equation that captures the dynamic evolution of novel morphologies in curvilinear domains using a polar coordinate system. Lamella-induced electric field alignment is demonstrated, with confinement domains and transition mechanisms between concentric and radial orientation depending on electric field intensity. The competition between electric field-driven ordering and geometric confinement provides insight into the alignment control of coherent lamellar morphology under spatial confinement. Observations have shown that the weak electric field is insufficient to overcome the frustration caused by thermal fluctuations and curvature. Also, excessively strong electric fields induce kinetic trap systems in metastable states with persistent defects. An optimal balance between defect relaxation and electrostatic driving is provided by an intermediate electric field strength, resulting in a defect-free, aligned lamellar morphology.