The reaction of N-2-aminoethyl-3-aminopropyltrimethyoxysilane (en-silane) with the surface of controlled pore glass (CPG) in aqueous solution was examined. The reaction appears to involve the rapid (ca. l min) formation of a covalently bound monolayer of en-silane at room temperature. Multilayers of bound polymeric en-silane can be obtained by reaction at elevated temperature. The latter reaction is slower, presumably because of the more stringent steric requirements of polymer formation in chain growth away from the CPG surface. For en-silane coverages ranging from 1.7 to 8.5 μ mol m-2, the mechanism for the complexation of copper(II) by ethylenediamine (en) bound to a CPG surface by reaction of en-silane with CPG was also investigated by thermometric and potentiometric titrimetry. A two-step mechanism is proposed. The data indicate that the first step of the surface reaction involves formation of a Cu(en)4 complex as opposed to the Cu(en) complex formed in the first step of the solution reaction. The second step results in a complex similar to the Cu(en)2; species formed in solution.
Bibliographical noteFunding Information:
R. J. K. acknowledges the financial support of the 3M Company and the Graduate School of the University of Minnesota in the form of fellowships. This research was supported in part by a grant from the National Institutes of Health (grant ROl-GM27581-Ol), and acknowledgement is made to the donors of the Petroleum Research Fund, administered by the ACS, for partial support (grant 10733-G3). We acknowledge the important contribution of a reviewer in suggesting the need for consideration of polymer formation in this system by virtue of the preparation procedures employed.