Curvature as a guiding field for patterns in thin block copolymer films

TL;DR

This paper investigates how curvature influences the orientation and stability of block copolymer patterns in thin films, revealing that curvature can be used to control pattern alignment and stability.

Contribution

The study combines symmetry analysis and numerical modeling to explain curvature-driven pattern alignment and stability in thin block copolymer films, aligning with experimental observations.

Findings

BC cylinders align along curvature at high curvatures

Transition from perpendicular to parallel alignment in supported films at low curvatures

Curvature can be used to manipulate and align BC patterns

Abstract

Experimental data on thin films of cylinder-forming block copolymers (BC) -- free-standing BC membranes as well as supported BC films -- strongly suggest that the local orientation of the BC patterns is coupled to the geometry in which the patterns are embedded. We analyze this phenomenon using general symmetry considerations and numerical self-consistent field studies of curved BC films in cylindrical geometry. The stability of the films against curvature-induced dewetting is also analyzed. In good agreement with experiments, we find that the BC cylinders tend to align along the direction of curvature at high curvatures. At low curvatures, we identify a transition from perpendicular to parallel alignment in supported films, which is absent in free standing membranes. Hence both experiments and theory show that curvature can be used to manipulate and align BC patterns.