Vesicle-to-cubosome transition from the solution self-assembly of branched-linear block copolymers triggered by the salting-out effect of Li ions

Abstract

The control of morphologies of soft nanostructures formed by the solution self-assembly of block copolymers (BCPs) is of significance for a spectrum of applications. In particular, non-synthetic pathways to maneuver the morphological transformation from the self-assembly of a single BCP have been of utmost interest because of the ability to achieve desired morphologies with minimal laborious synthesis. Herein, we report the Li ion-induced morphological transition of polymersomes of branched-linear BCPs composed of tri-arm polyethylene glycol (PEG) hydrophilic blocks and linear polystyrene (PS) blocks. The addition of lithium ions resulted in morphological transformation from polymersomes to inverse bicontinuous and cylindrical structures including polymer cubosomes and hexosomes, respectively. The extent of the salting-out effect resulting in the self-assembled morphologies can be tuned by varying the architecture and end-group functionalized hydrophilic segments in the BCPs. Our results could provide a rationale to design amphiphilic block copolymers to allow morphological transitions of solution self-assembled BCP nanostructures in the presence of ions.

Keywords

• Block copolymers
• Solution self-assembly
• Polymersomes
• Polymer cubosomes
• Salting-out effect