EPR spectroscopic investigation of the sol-gel transition in modified tetraethylorthosilicate gels.
Cu(2+) ions are used to follow the sol-gel transition in amino-modified TEOS mixtures. In contrast to unmodified TEOS gels, fixation of the spin probe (Cu(2+)) to the sol particle surface takes place and changes in mobility are detectable. Furthermore, we find changes in the coordination sphere of the copper ions and a temporary loss of EPR intensity. By using a simple kinetic model it is possible to estimate the rate constants of the condensation and syneresis processes.
Breyer
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Institute of Physical Chemistry, Lessingstrasse 10, D-07743 Jena, Germany.
Breitbarth
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FW
Vogelsberger
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