The Process-Directed Self-Assembly of Block Copolymer Particles

TL;DR

This study uses dynamic self-consistent field theory to explore how block copolymer particles form and change shape under different conditions, revealing pathways for controlled nanostructure design.

Contribution

It introduces a process-directed self-assembly mechanism for BCP particles, predicting shape transitions and internal structural evolution through a theoretical framework.

Findings

Reversible shape transition between onion-like and striped ellipsoids by temperature regulation.

Identification of a two-stage microphase separation process in onion-like particle formation.

Kinetic pathways for shape transformation among different BCP particle morphologies.

Abstract

The kinetic paths of structural evolution and formation of block copolymer (BCP) particles are explored using dynamic self-consistent field theory (DSCFT). It is shown that the process-directed self-assembly of BCP immersed in a poor solvent leads to the formation of striped ellipsoids, onion-like particles and double-spiral lamellar particles. The theory predicts a reversible path of shape transition between onion-like particles and striped ellipsoidal ones by regulating the temperature (related to the Flory-Huggins parameter between the two components of BCP, \chi_{AB}) and the selectivity of solvent toward one of the two BCP components. Furthermore, a kinetic path of shape transition from onion-like particles to double-spiral lamellar particles, and then back to onion-like particles is demonstrated. By investigating the inner-structural evolution of a BCP particle, it is identified that changing the intermediate bi-continuous structure into a layered one is crucial for the formation of striped ellipsoidal particles. Another interesting finding is that the formation of onion-like particles is characterized by a two-stage microphase separation. The first is induced by the solvent preference, and the second is controlled by the thermodynamics. The findings lead to an effective way of tailoring nanostructure of BCP particles for various industrial applications.