Chemical reactivity of amino-functionalized mesoporous silica thin films obtained by co-condensation and post-grafting routes

A. CALVO; M. JOSELEVICH; G. J. A. A. SOLER-ILLIA; F. J. WILLIAMS

MICROPOROUS AND MESOPOROUS MATERIALS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2009 vol. 121 p. 67 - 72

1387-1811

Amino-functionalized mesoporous hybrid thin films were synthesized by co-condensation and post- grafting routes. These materials were characterized by X-ray photoelectron spectroscopy (XPS), small angle X-ray scattering (SAXS-2D), X-ray reflectometry (XRR) and transmission electron microscopy (TEM). The chemical reactivity of the amine functional groups was determined via amidation with trifluo- roacetic acid anhydride and characterized with XPS and contact angle measurements. We found that the amidation reaction proceeds successfully in both cases showing that the amine functionalities are avail- able for reaction in the films obtained by both synthesis routes. However we also found that the fraction of amine functionalities available for reaction depends strongly on the functionalization route: 􏰀37% of amine functional groups are available for reaction in post-grafted films whereas 􏰀16% of them are avail- able in co-condensed films. This difference can be rationalized in terms of the different nature of the syn- thesis routes employed as in co-condensed films a fraction of amine functions are contained within the oxide backbone and thus unavailable for reaction. Our findings are important in the designed of func- tional materials where chemical functionalization might be a crucial step.