Gels of zirconium phosphate in organic solvents and their use for the preparation of polymeric nanocomposites

Abstract

Gels of α-zirconium phosphate (α-ZrP) in water have been prepared by exfoliation of crystalline α-ZrP induced by intercalation–deintercalation of propylamine. Although these gels are X-ray amorphous, their Raman spectra indicate that the α-type layers of the starting material remain essentially unaltered. Replacement of gel water with water miscible organic solvents has allowed the formation of α-ZrP gels in a great variety of solvents, such as alkanols, N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), acetone, tetrahydrofuran (THF) and even chloroform. Particular attention has been devoted to α-ZrP gels in DMF. On the basis of the surface area of the dry gels, the average thickness of the particles of exfoliated α-ZrP has been estimated between 25 and 80 nm for α-ZrP percentages in the starting gels between 2.5 and 10 wt%, respectively, in agreement with SEM images. α-ZrP gels in THF have been used for the preparation of polystyrene/α-ZrP nanocomposites with filler loadings up to 8 wt%. The presence of exfoliated α-ZrP delays the beginning of thermal decomposition of the polymer by a maximum of 45 °C for 4 wt% filler loading. The state of filler exfoliation has been confirmed by transmission electron microscopy.