Hyperuniform Structure in Polymer-Grafted Nanoparticle Assemblies

The study of relationships between order and disorder in materials across length scales has been an active topic of research in materials science and finds roots in many natural structures. In addition to ordered structures, exotic disordered states such as those exhibited in hyperuniform materials are also of recent interest. Hyperuniformity in two phase materials is defined by the presence of local disorder, in this respect similar to amorphous materials, but also with highly suppressed long range density fluctuations, similar to crystals. In the field of nanocomposite materials, the particle packing is an important parameter that can be altered to improve or control material properties. With their negligible density fluctuations at long length scales, hyperuniform packing structures exhibit efficient control of electromagnetic and/or mechanical waves. Here we demonstrate the fabrication of hyperuniform polymer grafted nanoparticle thin films using additive polymer processing techniques and characterize their resulting mechanical properties. The degree of hyperuniformity is then correlated to the mechanical properties of the composite determined by Brillouin light scattering and crazing experiments on lattice supports. At fixed polymer molecular weight we find that a bimodal distribution of gold nanoparticle diameters could be used to influence the strength of hyperuniformity. The concepts applied here are expected to influence the design of future component-level materials and structures.