Geometric properties of micelles formed by triblock copolymers and solubilizates in dilute solutions

In this work we study the geometric properties of the triblock copolymer micelles with solubilized low-mass molecules in a selective solvent using the Monte Carlo technique on a cubic lattice. The triblock copolymers are of the ABA type, with the two insoluble blocks at the ends. The size of the micelles is characterized by the squared radius of gyration of the micellar core, R_g², while the shape is treated by the asphericity b and the acylindricity c, which are defined in terms of the principal moments of the radius of gyration tensor. The parameters varied are the amount of solubilizate molecules, the polymer concentration, the interaction parameters between A and B, A and solvent, solute and solvent, solute and B block, and the A and B block length. The micelle size, characterized by R_g², grows with increasing concentration of the solubilizates and/or the polymer, and stronger interactions between the incompatible species. The A block length is found not to modify R_g² monotonously, while an increase in B block length results in a decrease in R_g² at high concentrations. As the size expands, the micellar shape becomes less spherical but retains its cylindricity. In addition to an increase in the averaged R_g², the distribution of R_g² becomes broader and the system less homogeneous.