The novel polymerizable -ketophosphonic acids 4, 8, 10, and 16 as well as the 9-(methacryloyloxy)-nonylphosphonic acid 20 were synthesized in four to eight steps. They were characterized by H-1 NMR, C-13 NMR, and P-31 NMR spectroscopy and by high-resolution mass spectra. The free-radical polymerization of 4, 8, 10, and 16 was carried out in a water/ethanol solution, using 2,2-azo(2-methylpropionamidine)dihydrochloride as initiator. To evaluate the reactivity of the acidic monomers 4, 8, 10, 16, and 20, their photopolymerization behavior was investigated by photodifferential scanning calorimeter. Copolymerizations with 2-hydroxyethyl methacrylate, glycol dimethacrylate, and N,N-diethyl-1,3-bis-(acrylamido)propane were studied. The homopolymerization of the corresponding -ketophosphonates and their copolymerization with hydroxyethyl methacrylate were also carried out. Self-etch adhesives based on the -ketophosphonic acids 4, 8, 10, and 16 were able to provide high shear bond strengths (SBSs) of dimethacrylate-based composite to dentin and enamel. The -ketophosphonic acid 8 was also shown to exhibit significantly better adhesive properties than the corresponding phosphonic acid 20. Indeed, the presence of the carbonyl moiety in the -position of the phosphonic acid group led to a strong improvement of the composite SBS to dentin and enamel. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3550-3563