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

The reactivity of bisphenol A (BPA), diethylstilbestrol (DEST) 2,2'-bipheno l (22'BP), 4,4'-biphenol (44'BP) and hydroquinone (HQ) as radical scavenger s was examined in 2,2'-azobisisobutyronitrile (AIBN)- and benzoyl peroxide (BPO)-induced methyl methacrylate (MMA) polymerization with respect to kine tic considerations. The initial rate of polymerization (IRP) was found to d ecrease in the order: 44'BP > BPA, DEST > 22'BP much greater than 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) much great er than 22'BP (0.8). It was found that BPA was a more highly efficient inhi bitor than HQ and that HQ acts as a retarder at higher concentrations in th e BPO system. The high activity of BPA indicated that BPA is probably oxidi zed by a radical interaction in the dental resin system. (C) 2000 Elsevier Science Ltd. All rights reserved.