Abstract
The relationship between the polymerization and the monomer structure of various dimethacrylates was investigated utilizing differential scanning calorimetry. Five ethyleneglycol dimethacrylates, three alkyleneglycol dimethacrylates, urethane dimethacrylate (UDMA) and 2, 2-bis[4(3-methacryloxy-2-hydroxypropoxy)phenyl]propane (Bis-GMA) was used. The polymerizations were isothermally conducted in sealed aluminum pans at the temperatures of 70℃, 80℃, 90℃, 100℃ and 110℃.
The thermogram of the dimethacrylates in isothermal bulk polymerization exhibited several exothermic peaks and the rate and extent of polymerization obtained from the thermogram increased with the increase of the polymerization temperature. The rate and extent of polymerization of the ethyleneglycol dimethacrylates were obviously dependent on the monomer structure, that is, the rate of polymerization increased with the decrease of the chain length between both two functional groups and the extent of polymerization increased with the increase of the chain length, while, no obvious dependence on the monomer structure was observed in the alkyleneglycol dimethacrylates under the conditions used. UDMA showed the highest rate of polymerization at all temperatures examined, and nonaethyleneglycol dimethacrylate showed the highest extent of polymerization of all the dimethacrylates. Both the rate and extent of polymerization of Bis-GMA were the lowest among the dimethacrylates.
