Shape control of soft patchy nanoparticles under confinement

Abstract

Molecular building blocks undergoing a hierarchical assembly process form nano-scale objects which can further assemble into supramolecular structures. When the intermediate units have a limited valence in bonding, complex structures with tailored properties can be created. Here, we consider a composite, star-shaped particle made of f diblock copolymer chains uniformly grafted on a spherical colloid and investigate its first self-assembly stage both in the bulk and under lateral confinement. By means of numerical simulations, we show that, in the bulk, this system develops aggregates whose number and size depend on the temperature as well as on the relative ratio of solvophobic monomers. The emerging aggregates are referred to as patches and impart directionality in bonding to the complex particle. We further characterize how we can control, by changing the lateral confinement, the shape of the brush and the patch properties as a function of the distance between the confining walls. We find that the number of the patches can be determined by tuning the degree of confinement imposed on the particle. Finally, we employ a continuum mechanics model, known as the Liquid Drop Model, to gain insight into the elastic properties of the system. This theoretical approach allows to connect the patch properties to the elastic response of the composite particle.