A reappraisal of the photopolymerization kinetics of triethyleneglycol dimethacrylate initiated by camphorquinone-N,N-dimethyl-p-toluidine for dental purposes

Abstract

This work describes the characteristics of triethyleneglycol dimethacrylate (TEGDM) polymerization when photoinitiated by camphorquinone (CQ) alone and in the presence of N,N-dimethyl-p-toluidine (DMT) in air and/or in N2. The rates of polymerization (RP), double bond conversion (p), monomer conversion (pm), temperature, and different concentrations of CQ and DMT were measured and analyzed. The second Rp maximum was found for the polymerization of TEGDM in the presence of CQ (without DMT) in N2 and in the presence of CQ + DMT in air. Formation of the second Rp maximum has been explained by the different mobility of the initiating monomer radicals in the polymer matrix as a polymerization proceeds. The 2,2,6,6-tetramethylpiperidine and 4-hydroxy-2,2,6,6-tetramethylpiperidinoxy radicals were used in order to evaluate the role of amineoxy and amineperoxy radicals in the polymerization of TEGDM in air. Finally, photophysical studies allowed a more detailed evaluation of the role of excited states of CQ and DMT in the photoinitiation process.