Real-time infrared spectroscopy (RT-FTIR) was used to study the effect of chemical structure of oligomer

reactive diluent and the ratio of oligomer and reactive diluent on the initiating activity of camphorquinone (CQ)/1

3-benzodioxole (BDO).The results showed that

urethane dimethacrylate (UDMA) with a low viscosity was prone to chain transfer reaction and had hydrogen donating ability.In the polymerization system with high content of UDMA

UDMA could be used as a competitive hydrogen donor to interact with the exited CQ

which significantly influenced the interaction of exited CQ and BDO.Another commercial oligomer 2

2-bis［4-(2-hydroxy-3-methacryloxypropoxy)phenyl］propane (bis-GMA) with a high viscosity exhibited a high reactivity.When it combined with reactive diluent triethylene glycol dimethacrylate (TEGDMA) in the formulation

a relatively less amount of TEGDMA

i.e.30%

could greatly reduce the viscosity of the monomer system and have little influence on the reactivity of Bis-GMA.At the same time

the Bis-GMA/TEGDMA (70/30

W/W) system with a lower viscosity could greatly improve the mobility of the free radical active species

which was beneficial to improve the initiating activity of CQ/BDO.