Micelle Formation of Diblock Copolymers Driven by Cononsolvency Effect

Abstract

This study utilizes self-consistent field theory to characterize various features of cononsolvency-driven spherical micelles formed by double hydrophilic block copolymers (DHBCs). Micelles are observed only at an intermediate cosolvent fraction, forming abruptly at a specific solvent/cosolvent mixing ratio and gradually disappearing with further cosolvent addition. A stronger core-block - cosolvent attractive interaction leads to a lower critical micelle concentration and a higher aggregation number. The density profile of cononsolvency-driven micelles is compared with that of conventional micelles, which form due to core-block - solvent repulsive interactions. In conventional micelles, the core is primarily occupied by polymer segments, whereas in cononsolvency-driven micelles, the core consists mainly of solvents and cosolvents. This fundamental difference can be explained through thermodynamic analysis. Conventional micelle formation is driven by the reduction of core-block - solvent contact due to repulsive interactions. In contrast, cononsolvency-driven micelle formation is governed by an increase in core-block - cosolvent contact area, playing the major role to minimize the total free energy-an essential distinction from conventional micelles.