Monomers for adhesive polymers. XV. Synthesis, photopolymerization, and adhesive properties of polymerizable β‐ketophosphonic acids

The novel polymerizable β‐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 ¹H NMR, ¹³C NMR, and ³¹P 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 β‐ketophosphonates and their copolymerization with hydroxyethyl methacrylate were also carried out. Self‐etch adhesives based on the β‐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 β‐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 β‐position of the phosphonic acid group led to a strong improvement of the composite SBS to dentin and enamel. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3550–3563