Publikation Detail

Abstract: Controlling the self-assembled nanoscale ionic aggregates in single-ion conducting polymers is a crucial step toward exceptional transport properties. We report a series of precisely-segmented polyethylene-like ionomers containing sulfonate groups (PES₂₃) with Li⁺, Na⁺, Cs⁺, or NBu₄⁺ counterions synthesized from step-growth polymerization. At room temperature, all polymers are semicrystalline with well-def̅ined nanoscale ionic layers separated by 35-38 Å, depending on the cation. In situ X-ray scattering measurements reveal that the layered ionic aggregates in PES₂₃Li, PES₂₃Na, and PES₂₃Cs transform, upon melting the PE blocks, into the 3 gyroid morphology. The gyroidal ionic aggregates in PES₂₃Li and PES₂₃Na further evolve into hexagonal symmetry as the temperature increases. These order-to-order transitions in ionic aggregate morphologies were also confirmed by oscillatory shear rheology. The ion transport behavior of these PES₂₃ polymers is strongly dependent on the ionic aggregate morphologies. Specifically, the 3D interconnected gyroid morphology of PES₂₃Li exhibits higher ionic conductivity than the isotropic layered or hexagonal morphologies. This innovative and versatile molecular design of ionomers leads to unprecedented percolated gyroidal ionic aggregate morphologies that provide a continuous pathway for improved ion transport.