Quantitative analysis of covalent bonding between substituted silanes and inorganic surfaces

Abstract

Diffuse reflectance Fourier transform infrared spectroscopy was used to study the interfacial chemical reaction between gamma-methacryloxypropyltrimethoxysilane and a low surface area particulate lead oxide. The surface reaction results in a covalent interfacial bond formed between the solid surface and the hydrolyzed alkoxysilane. Quantitative information about the interfacial bond is available from the spectra. Using digital subtraction techniques spectra of the adsorbate species and only the adsorbate/adsorbent interaction are produced. From these spectra it is possible to analyze quantitatively the covalent bonding between adsorbate and adsorbent at surface coverages near and much less than one equivalent molecular layer. Covalent bonding occurs with the substrate up to an adsorbate surface coverage of 1.50 mg/m2. The intensity of the interfacial covalent bond is linear with adsorbate concentration up to 1.50 mg/m2 and behaves similarly to theoretical prediction based on a simple model of bonded and non-bonded species. An example of the time-dependent formation of the adsorbate/adsorbent covalent bond is illustrated and suggests the ability to monitor kinetically the surface reaction. The loss of free hydroxyl groups on the substrate surface is also quantitatively monitored.