Self-Assembly and Transport in an Ionic Network based on a Double Helical Polymer

What happens when you combine ~10 vol% rigid charged rods with an ion-dense fluid? In at least one case, you organize the fluid into a rigid solid. We have been developing a new class of materials based on a highly charged double helical polyanion that can solidify a range of ion-containing fluids. We call these nematic physical networks molecular ionic composites (MICs). MICs are highly thermally stable, and can reach > 1 GPa tensile modulus and > 1 mS/cm ionic conductivity, and can incorporate a substantial loading of useful ions like Li⁺, Na⁺, or Zn²⁺. Although MICs are macroscopically solid, the nanoconfined and partially ordered ions inside move only modestly slower (a factor of 2-4) as compared to the neat precursor fluid. We can modulate the mechanical, transport, and chemical/thermal stability properties of MICs over wide ranges by changing the content and molecular weight of the polymer, and the chemistry of the ions and other mobile components. I will discuss the state of understanding of MICs, from the dependence of multi-scale network morphology and transport on composition, to the influence of specific molecular interactions and nanoconfinement on properties. I will also mention emerging applications of MICs in energy storage and molecular separations.