Layered perovskite nanosheets bearing fluoroalkoxy groups: their preparation and application in epoxy-based hybrids

Abstract

Nanosheets bearing CF₃(CF₂)₇C₂H₄O groups on their surface were prepared from a CF₃(CF₂)₇C₂H₄O derivative of ion-exchangeable layered perovskite HLaNb₂O₇·xH₂O (HLaNb) via exfoliation, and were further utilized to prepare epoxy-based hybrids. The CF₃(CF₂)₇C₂H₄O derivative of HLaNb (C10F_HLaNb) was prepared by reacting the n-decoxy derivative of HLaNb with 1H,1H,2H,2H-perfluorodecanol, CF₃(CF₂)₇C₂H₄OH. TEM and AFM observations revealed that the C10F_HLaNb was exfoliated into individual nanosheets bearing surfaces covered with CF₃(CF₂)₇C₂H₄O groups after ultrasonication in acetonitrile. The nanosheet dispersion in acetonitrile was employed to prepare epoxy-based hybrids, and the FE-TEM image of the epoxy-based hybrid with 5 mass% of the nanosheets (C10F_HLaNb/epoxy_5) showed that the nanosheets were dispersed in the epoxy matrix. Thermogravimetry of C10F_HLaNb/epoxy_5 and neat epoxy resin indicated that the initial mass loss due to water decreased and the thermal decomposition retarded by introducing C10F_HLaNb nanosheets. Dynamic mechanical thermal analysis revealed that the glass transition temperature of C10F_HLaNb/epoxy_5 (161 °C) was higher than that of neat epoxy resin (110 °C). These results clearly exhibit that thermal properties were improved by incorporating nanosheets bearing hydrophobic CF₃(CF₂)₇C₂H₄O groups in the epoxy resin most likely due to a decrease in water content. A water uptake test demonstrated that the water uptake rate of C10F_HLaNb/epoxy_5 was lower than that of the neat epoxy.