The impact of PEG bulk volume fraction on the interlayer distance of clay- PEG hybrids: Experimental and theoretical study

Abstract

The intercalation of polyethylene glycol (PEG) chains, in the inter-layer environment of the clay from Meknes, was performed using the direct intercalation method in the presence of water as a solvent. X-ray diffraction (XRD) technique was applied to follow the evolution of interlayer distances as a function of PEG bulk volume fraction. The XRD data assert the formation of an intercalated structure through the displacement of the peaks, which characterize the clay minerals towards the small and large angles. The evolution of the d001-spacing for the three classes of clays was similar. Indeed, as φ increases, the d001 variation is marked by two depletion phenomena due to the magnitude of the gyration radius compared to the inter-layer distance of the clay minerals. The plateau regime, characterized by the weak insertion of the chains, appears after each depletion/expansion cycle, which reveals a succession of the depletion-adsorption-plateau phenomenon. Based on the results of the XRD method, we proposed a model for the insertion of PEG chains in monolayer and bilayer forms into the interlayer environment of clay minerals. Finally, the scaling theory reveals a good agreement with the experimental findings and perfectly illustrates the succession of three regimes: dilute, bidimensional semi-dilute, and plateau.