Self-Consistent-Field Study of the Alignment by an Electric Field of a Cylindrical Phase of Block Copolymer

TL;DR

This study uses Self-Consistent Field Theory to analyze how electric and surface fields influence the orientation of cylindrical block copolymer phases, revealing phase transitions and boundary layer effects.

Contribution

It provides a detailed numerical analysis of phase behavior and boundary effects in cylindrical block copolymer films under electric and surface fields.

Findings

Weak surface fields cause a direct transition from parallel to perpendicular cylinder alignment.

Stronger surface fields lead to an intermediate phase with interior cylinders aligned and boundary layers with hexagonal symmetry.

Boundary layers favoring the minority block form at the surfaces, affecting overall morphology.

Abstract

Self-Consistent Field Theory is applied to a film of cylindrical-forming block copolymer subject to a surface field which tends to align the cylinders parallel to electrical plates, and to an external electric field tending to align them perpendicular to the plates. The Maxwell equations and self-consistent field equations are solved exactly, numerically, in real space. By comparing the free energies of different configurations, we show that for weak surface fields, the phase of cylinders parallel to the plates makes a direct transition to a phase in which the cylinders are aligned with the field throughout the sample. For stronger surface fields, there is an intermediate phase in which cylinders in the interior of the film, aligned with the field, terminate near the plates. For surface fields which favor the minority block, there is a boundary layer of hexagonal symmetry at the plates in which the monomers favored by the surface field occupy a larger area than they would if the cylinders extended to the surface.