Disentangling the Role of Chain Conformation on the Mechanics of Particle Brush Materials

The modification of particle surfaces with polymeric ligands is widely used to enhance the interactions between particles, to allow their integration in polymeric matrices or for the processing of particulate materials through techniques such as molding or extrusion. A critical question that is of both fundamental and applied relevance pertains to the role of polymer architecture in controlling the interactions and resulting mechanical properties of polymer-tethered particles. Because of its ability to resolve the mechanical characteristics on submicrometer scale without sample destruction, Brillouin light scattering (BLS) has become an important analytical tool to elucidate the connection between structure, dynamics and macroscopic response in hybrid material systems. In this contribution a combined approach of experimental BLS analysis and coarse-grained simulations is presented to identify the respective contribution of grafting density and degree of polymerization on the macroscopic mechanical properties of films from polystyrene tethered silica colloids. The bulk modulus is maximized in intermediate to low grafting density systems, where the hard silica cores are partially exposed due to conformational fluctuations of the grafted polymers.