Preparation of Organic−Inorganic Hybrids Possessing Nanosheets with Perovskite-Related Structures via Exfoliation during a Sol−Gel Process

Abstract

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.