Kinetic evaluation of reactivity of bisphenol A derivatives as radical scavengers for methacrylate polymerization.

The reactivity of bisphenol A (BPA), diethylstilbestrol (DEST) 2,2'-biphenol (22'BP), 4,4'-biphenol (44'BP) and hydroquinone (HQ) as radical scavengers was examined in 2,2'-azobisisobutyronitrile (AIBN)- and benzoyl peroxide (BPO)-induced methyl methacrylate (MMA) polymerization with respect to kinetic considerations. The initial rate of polymerization (IRP) was found to decrease in the order: 44'BP > BPA, DEST > 22'BP >> HQ, while the stoichiometric factor (n) of free radicals trapped by phenolic moiety decreased in the order: 44'BP (2.3) > HQ (2.0) > BPA, DEST (1.8) >> 22'BP (0.8). It was found that BPA was a more highly efficient inhibitor than HQ and that HQ acts as a retarder at higher concentrations in the BPO system. The high activity of BPA indicated that BPA is probably oxidized by a radical interaction in the dental resin system.