Self-Assembly of Gyroid-Forming Diblock Copolymers under Spherical Confinement

Abstract

The self-assembly of gyroid-forming diblock copolymers (diBCPs) confined in spherical cavities was systematically investigated by simulations and experiments. The Monte Carlo simulations were carried out on the single-site bond fluctuation model of two gyroid-forming diBCPs of different volume fractions using the simulated annealing method. The experimental study was performed on gyroid-forming poly(styrene)-b-poly(lactic acid) diBCPs confined in spherical cavities. The cavities were fabricated through the assembly of polystyrene colloids to form opal structures, followed by replacement to form inverse opal structures. The surface of the cavities was composed of hydrophobic polyurethane acrylate and hydrophilic SiO2, providing confining surfaces with a different preference for specific polymeric blocks. It was observed from both the experiments and simulation that, depending on the conditions of spherical confinement, a rich array of nanostructures was self-assembled from the gyroid-forming diBCPs. The morphological predictions of simulations are qualitatively consistent with the experimental observations. The self-assembled structures depend sensitively on the surface selectivity and the degree of confinement quantified by the ratio D/L0, where D and L0 are the spherical diameter and period of the equilibrium gyroid phase, respectively. The formed nanostructured self-supporting spheres have considerable potential for applications in drug release, catalysts, optoelectronic devices, filters, and other applications.