Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals

Significance Polymer nanocomposites containing nanoparticle fillers often have enhanced strength, stiffness, and toughness that are highly dependent on nanoparticle spatial distribution, which can be challenging to control in the limit of high nanoparticle loading. Solid superlattices formed from close-packed, ligand-coated inorganic nanocrystals can have high stiffness and large elastic recovery, although nanocrystals interact solely through van der Waals forces. We use polymer-grafted nanocrystals to make superlattices with versatile structural architecture and dimensions to investigate the effects of structural defects, film thickness, and polymer length on mechanical behavior. We find that the elastic response of the superlattice is large even when the arrangement of nanocrystals within the superlattice is perturbed, and that polymer conformation plays a large role in determining mechanical properties.