Self-Assembly of Asymmetrically Interacting ABC Star Triblock Copolymer Melts

TL;DR

This study uses self-consistent field theory to explore the complex phase behavior of asymmetrically interacting ABC star triblock copolymer melts, revealing a rich variety of stable structures and expanding understanding beyond equal interaction systems.

Contribution

It introduces a detailed SCFT analysis of asymmetric ABC star triblock copolymers, predicting a complex phase diagram with fifteen stable ordered phases, including hierarchical structures.

Findings

Fifteen stable ordered phases identified.

Hierarchical structures form near B-rich corner.

Good agreement with experimental results.

Abstract

The phase behavior of asymmetrically interacting ABC star triblock copolymer melts is investigated by the self-consistent field theory (SCFT). Motivated by the experimental systems, in this study, we focus on the systems in which the Flory-Huggins interaction parameters satisfy $\chi_{AC}>\chi_{BC}\approx \chi_{AB}$. Using various initialization strategies, a large number of periodic structures have been obtained in our calculations. A fourth-order pseudospectral algorithm combined with Anderson mixing method is used to compute the free energy of candidate structures carefully. The stability has been detailedly analyzed by splitting the free energy into internal and entropic parts. A complete and complex triangular phase diagram is presented for a model with $\chi_{AC}>\chi_{BC}= \chi_{AB}$ in which fifteen ordered phases, including two-, and three-dimensional structures, have been predicted to be stable from the SCFT calculations. Generally speaking, with the asymmetrical interactions, the hierarchical structures tend to be formed near the B-rich corner of the triangular phase diagram. This work broadens the previous theoretical results from equal interaction systems to unequal interaction systems. The predicted phase behavior is in good agreement with experimental observations and previous theoretical results.