Organic derivatives of the layered perovskite HLaNb₂O ₇·xH₂O with polyether chains on the interlayer surface: Characterization, intercalation of LiClO₄, and ionic conductivity

Polyether chains have been successfully grafted onto the interlayer surface of a Dion-Jacobson-type layered perovskite, HLaNb₂O ₇·xH₂O, by a reaction between an n-decoxy-derivative of HLaNb₂O₇·xH₂O and CH₃(OCH₂CH₂)_mOH (1 ≤ m ≤ 4). After the reaction, the interlayer distance decreases from 2.73 nm to 1.58 (m = 1), 2.07 (m = 2), 2.28 (m = 3), and 2.69 (m = 4) nm. Solid-state ¹³C CP/MAS NMR spectroscopy indicates that the CH₃(OCH₂CH ₂)_mO- groups are bound to the interlayer surface of HLaNb₂O₇·xH₂O. The n-decoxy groups are completely removed by the reaction with CH₃(OCH₂CH ₂)_mOH (m = 2 and 3), while a part of the n-decoxy groups remain after the reaction with CH₃(OCH₂CH ₂)_mOH (m = 1 and 4). Upon treatment of the CH ₃(OCH₂CH₂)_mO-grafted HLaNb ₂O₇·xH₂O (m = 2 or 3) with a CH ₃(OCH₂CH₂)_mOH solution of LiClO ₄, the interlayer distance decreases further to 1.78 (m = 2) and 2.01 (m = 3) nm. Inductively coupled plasma emission spectrometry reveals the presence of lithium (0.22 (m = 2) and 0.24 (m = 3) per [LaNb₂O ₇]). The presence of ClO₄^- ions is demonstrated by Raman spectroscopy, and the position of the ν₁(A₁) band indicates the presence of isolated ClO₄^- ions in the interlayer space. After treatment with a LiClO₄ solution, CH ₃(OCH₂CH₂)_mO-grafted HLaNb ₂O₇·xH₂O (m = 2 and 3) exhibits ionic conductivity, and no clear temperature dependence is observed.