New Radiopaque Bromine‐Containing Monomers for Dental Restorative Materials

Four bromine‐containing methacrylates 1 – 4 are synthesized from pentaerythritol tribromide and 2,2,2‐tribromoethanol and are characterized by ¹H and ¹³C NMR spectroscopy. Their free radical polymerization is performed in dimethylformamide (DMF), using 2,2′‐azobis(2‐methylpropionitrile) as initiator. The photopolymerization behavior of monomers 1–4 is investigated using a differential scanning calorimeter. Homopolymerizations and copolymerizations with 2‐hydroxyethyl methacrylate are carried out. Both the presence of a carbamate group and of bromine atoms result in an increase of the polymerization rate. Dental resins are prepared by replacing a certain amount of 2‐(4‐cumyl‐phenoxy)ethyl methacrylate by monomers 3 and 4 in a model formulation. The incorporation of these methacrylates leads to a significant increase of the radiopacity. Resins based on mono­mer 4 exhibit improved mechanical properties.