Morphology Inversion Induced by Stimuli-responsive Blocks in the AB/BC Block Copolymer Assemblies in Solution

Abstract

Co-assembly of different block copolymers has emerged as a versatile strategy for constructing stimuli-responsive polymer nanostructures with broad applications in biomedicine. However, the spatial distribution of functional blocks and the structural transition of mixed assemblies under external stimuli remain insufficiently explored, limiting the rational design of efficient delivery systems with on-demand cargo loading and release. Here, we systematically investigated the self-assembly behaviors of AB/BC mixture in solution using the dissipative particle dynamics (DPD) method. By varying the interaction parameters between different components, several classic morphologies were obtained, including vesicles (V), multicompartment vesicles (MCV), and large compound micelles (LCM). Most importantly, the distinct hydrophilic blocks (A/C) underwent microphase separation during the co-assembly process, yielding aggregates with patterns having different internal A/C distributions, such as mixed, Janus (J), and A- or C-dominated (A/C) vesicles. Upon applying external stimuli, we tracked the dynamic rearrangement process of blocks A and C, focusing on the inversion of the dominant internal block. The results revealed that kinetic factors significantly influence the inversion process, either accelerating, decelerating, or even freezing the structure. A kinetic-control mechanism for the inversion was proposed, wherein the mobility of the hydrophilic blocks and the barrier effect of the hydrophobic layer can be tuned by adjusting the interaction parameters (such as a_BC and a_BS), thereby governing the occurrence and kinetics of inversion. These findings can provide valuable insights into the precise modulation of block distribution and rearrangement in stimuli-responsive aggregates, offering applications in controlled drug delivery and release processes.