Accession Number : ADA290589

Title :   Cage-Like Precursor Formation from Extensive Cyclization in Sol-Gel Inorganic Condensation Polymerization.

Descriptive Note : Technical rept.,

Corporate Author : MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE

Personal Author(s) : Ng, L. V. ; Thompson, P. ; Sanchez, J. ; McCormick, A. V.

PDF Url : ADA290589

Report Date : 19 JAN 1995

Pagination or Media Count : 15

Abstract : In the sol-gel synthesis of silica by the acid catalyzed hydrolysis and condensation of tetraethyl orthosilicate (TEOS), the fractal dimension, density and homogeneity of the gel depends strongly on the reaction conditions such as the pH and water concentration. However 29Si NMR results have shown that gelation occurs consistently at 80% conversion. The 80% gel conversion is very high compared to the 30% predicted by random branching theory. These results suggest that cyclization is strongly favorable, forming, typically, the most compact three-dimensional cage-like precursor of expected diameter around 10A. (jg)

Descriptors :   *POLYMERIZATION, *CONDENSATION, *INORGANIC MATERIALS, FRACTALS, METALS, DENSITY, NUCLEAR MAGNETIC RESONANCE, SIZES(DIMENSIONS), SILICON DIOXIDE, WATER, PRECURSORS, RESPONSE, SILICON, ORGANIC COMPOUNDS, HYDROLYSIS, GELS, PH FACTOR, CONCENTRATION(CHEMISTRY), HOMOGENEITY, ACIDS, BASES(CHEMISTRY), ALKOXY RADICALS, GELATION, SILICA GELS.

Subject Categories : Polymer Chemistry
      Inorganic Chemistry
      Organic Chemistry
      Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE