Synthesis and photopolymerization of new dental monomers from o-hydroxyaryl phosphonates

Novel aromatic mono- and diphosphonate monomers based on t-butyl alpha-bromomethaerylate were prepared for use in dental composites. The synthesis of the two monomers involved three steps: the reaction of diethyl phosphite with phenol or hydroquinone, the rearrangement of the resulting phosphate derivatives into o-hydroxyaryl phosphonates with lithium diisopropylamide, and the reaction of o-hydroxyaryl phosphonates with t-butyl alpha-bromomethacrylate. Then, the selective hydrolysis of the t-butyl ester groups of the monomers with trifluoroacetic acid gave the other carboxylic acid containing monomers. The photopolymerization behaviors of the synthesized monomers with glycerol dimethacrylate and triethylene glycol dimethacrylate were investigated with photodifferential scanning calorimetry at 40 degrees C with 2,2'-dimethoxy-2-phenyl acetophenone as the photoinitiator. The hydrolysis of the t-butyl groups of the monomers increased the reactivity and the rates of polymerization of the monomers. The mixtures of the acid monomers showed rates of polymerizations similar to those of homopolymerizations of triethylene glycol dimethacrylate and glycerol dimethacrylate. (c) 2006 Wiley Periodicals, Inc.