Surface modification. II. Functionalization of solid surfaces with vinylic monomers

A new method to functionalize surfaces of solid substrates such as glass, silicon crystals, and silica microspheres with appropriate vinylic monomers, i.e., methyl vinyl ketone, methyl acrylate, metbacrolein, and acrolein, is described. The surface modification process was performed through the following sequence of reactions: (a) derivatization of the surfaces with ω-nitrile groups by interacting the substrates with SiCl₃(CH₂)₃CN; (b) subsequent reduction of the ω-nitrile groups with diborane to ω-amine groups; (c) binding of the vinylic monomers to the surfaces via the ω-amine groups. pK_1/2 of the surface primary amine groups, as determined by contact angle titration, was found to be 2-4 units lower than the pK₄ values of primary amine analogous in solution. Methyl vinyl ketone and methyl acrylate were covatently bound to the amine surfaces only under basic conditions via the Michael addition reaction. Methacrolein and acrolein were covalently bound to the amine surfaces under both acidic and basic conditions, via two major reactions: the Michael addition reaction and Schiff base bond formation. The concentration of the aldehyde groups of the surfaces obtained by the reaction with methacrolein and acrolein was significantly higher than that obtained using the common, published method in which glutaraldehyde interacts with the amine surfaces.