Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2–3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3.
Munirathinam, R., Ricardi, R., Egberink, R. J. M., Huskens, J., Holtkamp, M., Wormeester, H., ... Verboom, W. (2013). Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor. Beilstein journal of organic chemistry, 9, 1698-1704. https://doi.org/10.3762/bjoc.9.194