Fast Potassium Ion Transport in Sub-1 nm Pores of Self-Assembled Polymer Membranes Derived from Linoleic Acid

The transport of ions in nanoporous polymers is central to the development of membranes for electrochemical devices. Herein, we fabricate highly ordered nanoporous polymers by self-assembling and cross-linking conjugated linoleic acid and study the transport of potassium ions in the resulting uniform, sub-1 nm pores. The system features a transport limiting dimension of 0.65 nm, with 0.70 nm separating the carboxylate headgroups on the pore walls. Despite the small pore size relative to hydrated K +, we observe K + conductivities of 1 and 10 mS cm –1 at 50% and 80% relative humidity (RH) at 30 °C, respectively. The activation energy at 80% RH is only ≈1.5× that for K + conduction in the bulk electrolyte, suggesting that confinement and ion pairing do not significantly hinder transport. The well-defined pore size and appreciable conductivities may enable the use of such sustainably derived membranes in electrochemical devices where size-based discrimination of species is required.