Preparation of organic-inorganic hybrids possessing nanosheets with perovskite-related structures via exfoliation during a sol-gel process

Organic-inorganic hybrids containing exfoliated nanosheets with a perovskite-related structure have been prepared from an n-decoxy derivative of an ion-exchangeable layered perovskite, HLaNb₂O₇· xH₂O (HLaNb) or HCa₂Nb₃O₁₀· xH₂O (HCaNb), silanol-terminated poly(dimethylsiloxane) (PDMS), and tetramethoxysilane (TMOS) via a sol-gel process involving the reaction of the n-decoxy derivative with a PDMS-TMOS mixture and subsequent intentional hydrolysis with hydrochloric acid. The X-ray diffraction (XRD) patterns of the resultant products after intentional hydrolysis indicate both preservation of the perovskite-like slab structure and disappearance of stacking order. Partial exfoliation of layered perovskites is correspondingly observed by transmission electron microscopy (TEM). The formation of a polysiloxane network composed of PDMS chains and Qⁿ units ((RO)_4-nSi(OSi)_n: R = H, CH₃) via intentional hydrolysis is shown by the solid-state ²⁹Si CP/MAS (cross-polarization and magic angle spinning) NMR spectroscopy. These products are expected to possess the Nb-O-Si linkage interface since a signal assignable to the (SiO)Si(CH₃) ₂O-Nb environment is present in the ²⁹Si CP/MAS NMR spectra of products prepared from an n-decoxy derivative of HLaNb (or HCaNb), PDMS, and TMOS in a similar manner without intentional hydrolysis and the Nb-O-Si bonds are expected to be preserved during hydrolysis. The exfoliated structures should be formed during the intentional hydrolysis process since the products prepared without intentional hydrolysis clearly exhibit a stacking order along the c axis.