Revealing structure and dynamics in host–guest supramolecular crystalline polymer electrolytes by solid-state NMR: Applications to β-CD-polyether/Li+ crystal

Abstract

The detailed knowledge of the structure and dynamics in molecular level is very relevant for our understanding of the conductivity mechanism of solid state polymer electrolytes. In this work, we have synthesized two conductive β-CD-polyether/Li+ inclusion crystals, which both have the channel-like structure formed by the β-CDs, but differ by the chemical nature of the assembled polymer chains. 1H, 7Li and 19F solid state NMR have been performed to study the dynamics of the polymer chains, cations and anions. 1H NMR of the samples reveals the clear difference in the segmental mobility of the polymer chains threaded inside the β-CDs, depending on the chemical nature of the polymer chains. Temperature dependent solid-state 2D 7Li-7Li exchange NMR combined with 7Li finite-pulse radio frequency-driven recoupling (fp-RFDR) NMR reveals two different Li+ local exchange dynamics, namely, the Li+ exchange process between the different polymer chain segments and the Li+ exchange process between the polymer chains and the channels (i.e., the assembled β-CDs). 19F NMR of the samples reveals that the anions in the samples are in a relatively immobile state, indicating that the anions are well separated from the mobile Li+ ions in the samples. The implications of these NMR results for understanding of the conductivity mechanism of the materials are discussed.