Simulating Diblock Copolymer Micelles in Binary Explicit Solvents

Amphiphilic block copolymers form nanoscale assemblies when dissolved in a selective solvent. Such self-assembled structures have wide-ranging applications as drug delivery vehicles and nanoreactors, etc. A powerful method to manipulate the assemblies is to vary the composition of solvent mixtures. Unlike single solvent solution, computational studies of amphiphilic block copolymers in solvent mixtures are rarely reported due to high computational cost associated with the necessity of treating solvents explicitly. Here, the Field-Accelerated Monte Carlo [1] simulation is employed in the expanded grand canonical ensemble to study the micelle formation of diblock copolymers in binary solvents: one selective solvent and one good solvent for both blocks. We investigate effects of molecular weight and solvent composition on micelle morphology, critical micelle concentration, and micelle size and aggregation number. It is found that distribution of the good solvent is highly inhomogeneous, concentrating at micelle interface and partitioning unevenly outside/inside micelle cores. Solvent intake by micelle cores increases with polymer molecular weight, affecting the way micelle size and aggregation number change with solvent composition.

[1] J. Zong and D. Meng, submitted to J. Chem. Phy