Interplay of the structure and properties of hierarchical functional nanocomposites

Our recent work shows that membranes comprised solely of polymer grafted nanoparticles exhibit remarkable, enhanced, molecular transport compared to that of the corresponding bulk polymer or “traditional” ungrafted, mixed-matrix composites. At a fixed grafting density, these enhancements show a non-monotonic dependence on the grafted chain length. Extensive structural characterization in the dry (non-solvated) state indicate only monotonic changes to the interparticle spacing as a function of molecular weight. Additionally, in the swollen state, we observe homogeneous solvent distribution within the brush. Interestingly, the linear mechanical response of these materials show a liquid-to-solid transition, whose location coincides with the peak in permeability. These results demonstrate that rational design of hierarchical materials with desired functionalities relies heavily on control of structure-property relationships over multiple length scales.