N-alkyl-N-(phosphonoethyl) substituted (meth)acrylamides – new adhesive monomers for self-etching self-priming one part dental adhesive

Novel N-alkyl-N-(phosphonoethyl) substituted mono-, bis- and tris(meth)acrylamides 3 were synthesized by two different three-step reactions and characterized by IR, (1)H NMR and (13)C NMR spectroscopy as well as refractive index and viscosity. The phosphonoethyl substituted (meth)acrylamide monomers show improved hydrolytic stability compared to carboxylic esters. The highest stability was found for the phosphonoethyl substituted acrylamide monomers. Acrylamides have a larger polymerization enthalpy ranging from −50 to −70 kJ·mol(−1) per double bond compared to methacrylamides which show −8.57 to −25.1 kJ·mol(−1) per double bond. Depending on their structure (meth)acrylamides 3 exhibit an adhesion to enamel and dentin up to 19.5 MPa. The monomer 3c shows the highest adhesion values to both substrates, namely 15.3 ± 3.4 MPa to enamel and 18.5 ± 2.3 MPa to dentin.