Preparation and characterisation of α-layered zirconium phosphate sulfophenylenphosphonates with variable concentration of sulfonic groups
Abstract Zirconium phosphate sulfophenylenphosphonates of general formula Zr(HPO 4 ) 2− x (SPP) x · n H 2 O, with SPP = O 3 PC 6 H 4 SO 3 H and x in the range 0.4–1.35, were precipitated from solutions containing H 3 PO 4 , H 2 SPP and ZrF 6 2− . The SPP/HPO 4 ratio in the solids is equal to the H 2 SPP/H 3 PO 4 ratio in the starting solutions for x  ≤ 1 and lower for x  > 1. The results coming from 31 P MAS NMR, X-ray powder diffraction, FTIR-PAS spectroscopy and density measurements, as well as from the intercalation of α,ω-alkyl diamines in Zr(HPO 4 ) 1.00 (SPP) 1.00 , suggest that the solids have a layered structure built up by the packing of symmetric α-layers where SPP and HPO 4 groups are uniformly distributed on both layer faces. Proton conductivity, at 100 °C and 70% relative humidity, increases with x and reaches a maximum of 0.04 S cm − 1 for x  = 1.35. The conductivity of Zr(HPO 4 ) 0.65 (SPP) 1.35 · n H 2 O was determined as a function of the water content at 100 °C and compared with that of Nafion 117 and of a sulfonated polyetherketone.