Study on functionalization of metal surfaces. III. Photopolymerization of monomer films on metal surfaces

The three kinds of monomer films on metal surfaces were deposited by adsorption from a solution of 6‐polymerizable substituents‐1,3,5‐triazine‐2,4‐dithiol monosodium salts (RTDN); the polymerizable substituents such as cis‐9‐octadecenylamino, di(cis‐9‐octadecenyl)amino, and p‐vinylbenzyl(cis‐9‐octadecenyl)amino groups were selected in view of the polymerization activity of unsaturated groups in the substituents and the packing degree of monomer molecules. The monomer films were estimated to consist of mainly 6‐substituents‐1,3,5,‐triazine‐2,4‐dithione (3H, 5H) and to be multimolecular layers that are considerably cross‐packed and ordered. The monomer films on metal surfaces were polymerizable under a UV light irradiation in air atmosphere to give polymer films. In the photopolymerization, azobis(isobutyronitrile) (AIBN) was very effective for increasing the monomer conversion and the polymerization rate. The optimum concentration of AIBN in monomer films was very small, about 0.025 mol %. The monomer conversion was influenced by the kind of monomers, namely, the polymerization activity and the packing degree. The effect of the packing degree was especially remarkable. The monomer conversion decreased with an increase in the thickness of monomer films. This is because the polymerization was initiated by oxygen and AIBN, which were diffused into the inner of monomer films. The possibility of polymerization of the unsaturated groups and the thione groups in monomer molecules under UV light irradiation is discussed.