Morphologies and phase diagrams of ABC star triblock copolymers in cylindrical nanotubes with homogenous and patterned surfaces

Abstract

We investigate the morphologies of ABC star triblock copolymers in cylindrical nanotubes by applying real-space self-consistent mean-field theory. The nanotubes are designed to possess homogenous and patterned surfaces. Numerous directed morphologies with various symmetries, such as concentric lamella, discrete cylinder, asymmetric cylinder, Janus cylinder, ring disk, and double helix, are identified in the triangular phase diagrams constructed by block ratios. For the tubes with A-attractive homogenous surfaces, the phases are distributed with respect to the A-block ratio in the phase diagrams. By contrast, those of tubes with BC-attractive homogenous surfaces are distributed in a center-face manner in the phase diagrams. In the tubes with Janus patterned surfaces, frustration phases appear at the center of the phase diagrams. However, the phases that the morphologies accommodate to the Janus patterns occur near the edges of the phase diagrams. Furthermore, the chain conformations and phase transitions of these morphologies are analyzed and discussed by their segment distributions, free energies, internal energies and entropic energies. Simulation results predict the possibility of controlling the morphologies for triblock copolymers in long-range orders by adjusting the patterns in nonplanar templates.