Reactivity of Benzoyl Peroxide/Amine System as an Initiator for the Free Radical Polymerization of Dental and Orthopaedic Dimethacrylate Monomers: Effect of the Amine and Monomer Chemical Structure

The free radical homopolymerization of Bis-phenol-A-bis(glycidyl methacrylate) (Bis-GMA), a urethane dimethacrylate (UDMA), and triethylene glycol dimethacrylate (TEGDMA) induced by a benzoyl peroxide (BPO)/amine redox couple was studied by differential scanning calorimetry. As amine, para-substituted N, N -dimethylaniline derivatives were used. Amines with electron-donating para-substituents, such as −CH 3, −CH 2 CH 2 OH, or −CH 2 COOH, are efficient co-initiators for polymerization at 37 °C. On the contrary the amine with the electron-withdrawing para-substituent −COOCH 2 CH 3, could not initiate polymerization at 37 °C, but only at higher temperatures. The kinetic parameters of polymerization are strongly affected also by the chemical structure of the monomer. UDMA showed the highest values for the maximum polymerization rate followed by Bis-GMA and TEGDMA. TEGDMA showed the highest degree of final conversion (ca. 70%) followed by UDMA (ca. 40%) and Bis-GMA (ca. 27%).