Monomers for Adhesive Polymers, 9-Synthesis, Radical Photopolymerization, and Properties of (Meth)acrylamido Dihydrogen Phosphates

5‐Methacrylamidopentyl (3a), 10‐(N‐methylacrylamido)decyl (3b), or 11‐(N‐methylacrylamido)undecyl dihydrogen phosphate (3c) are synthesized by (meth)acrylation of the corresponding ω‐aminoalkane‐1‐ols with methacrylic anhydrid or acryloyl chloride followed by phosphorylation of the formed ω‐(meth)acrylamidoalkane‐1‐ols. The monomers show a significantly improved hydrolytic stability compared to the corresponding methacrylate‐based dihydrogen phosphates. The photopolymerization of 3a–c with a bis(acrylamide) crosslinker confirms a high reactivity in the free‐radical copolymerization. These monomers enable the mediation of a strong bond between the enamel or dentin surface and a restorative composite under self‐etching conditions. 5‐Methacrylamidopentyl, 10‐(N‐methylacrylamido)decyl, and 11‐(N‐methylacrylamido)undecyl dihydrogenphosphate are synthesized. The monomers are radically photopolymerizable, show improved hydrolytic stability and a low cytotoxicity, and can etch enamel and dentin. Therefore, they may be used as adhesive monomers in single‐bottle self‐etching enamel‐dentin adhesives.