Materials with controlled mesoporosity derived from synthetic polyvinylpyrrolidone-clay composites

Mesoporous synthetic days (MSCs) are obtained when polymer-containing silic ate 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 bro ad molecular weight and concentration ranges is achieved. The polymer loadi ng of synthesized composites is determined by thermal analysis, and the bas al spacing changes resulting from different levels of polymer intercalation are monitored by X-ray powder diffraction (XRD). In some cases, intercalat ion occurs to such a degree as to delaminate the layers and cause loss of s tacking registry. Polyvinylpyrrolidone (PVP) of several average molecular w eights ranging from 10 x 10(3)-1.3 x 10(6), in loadings varying from 10 to 20 wt.%, were used. The organic polymer template molecules were removed fro m synthetic polymer-clay complexes via calcination. Pore radii, surface are as and pore volumes of the resulting porous inorganic networks (MSCs) were then measured. A direct correlation between both PVP M-w and polymer loadin g on the radius of the average pore was found, which varied from 21-45 Angs trom. (C) 1999 Elsevier Science B.V. All rights reserved.