Materials with controlled mesoporosity derived from synthetic polyvinylpyrrolidone–clay composites

Abstract

Abstract Mesoporous synthetic clays (MSCs) are obtained when polymer-containing silicate gels are hydrothermally crystallized to form layered magnesium silicate hectorite clays containing polymers that are incorporated in situ. In this in situ technique, interlayer intercalation of different polymers over broad molecular weight and concentration ranges is achieved. The polymer loading of synthesized composites is determined by thermal analysis, and the basal spacing changes resulting from different levels of polymer intercalation are monitored by X-ray powder diffraction (XRD). In some cases, intercalation occurs to such a degree as to delaminate the layers and cause loss of stacking registry. Polyvinylpyrrolidone (PVP) of several average molecular weights ranging from 10×103–1.3×106, in loadings varying from 10 to 20 wt.%, were used. The organic polymer template molecules were removed from synthetic polymer–clay complexes via calcination. Pore radii, surface areas and pore volumes of the resulting porous inorganic networks (MSCs) were then measured. A direct correlation between both PVP Mw and polymer loading on the radius of the average pore was found, which varied from 21–45 A.