Nanoparticle Assembly in High Polymer Concentration Solutions Increases Superlattice Stability.

Polymer nanocomposites are made by combining a nanoscale filler with a polymer matrix, where polymer-particle interactions can enhance matrix properties and introduce behaviors distinct from either component. Manipulating particle organization within a composite potentially allows for better control over polymer-particle interactions, and the formation of ordered arrays can introduce new, emergent properties not observed in random composites. However, self-assembly of ordered particle arrays typically requires weak interparticle interactions to prevent kinetic traps, making these assemblies incompatible with most conventional processing techniques. As a result, more fundamental investigations are needed into methods to provide additional stability to these lattices without disrupting their internal organization. The authors show that the addition of free polymer chains to the assembly solution is a simple means to increase the stability of nanoparticle superlattices against thermal dissociation. By adding high concentrations (>50 mg mL ) of free polymer to nanoparticle superlattices, it is possible to significantly elevate their thermal stability without adversely affecting ordering. Moreover, polymer topology, molecular weight, and concentration can also be used as independent design handles to tune this behavior. Collectively, this work allows for a wider range of processing conditions for generating future nanocomposites with complete control over particle organization within the material.