Objectives . Photo-iniferters are molecules capable of initiation, chain transfer and termination reactions, suitable to produce controlled radical photo-polymerizations, which can be useful, for example, when thermal stability is desired. The objective of this study was to determine the influence of monomer structure/functionality on the affinity of the thiyl radical from the iniferters with the propagating carbon radical in methacrylates.
Materials and methods . Three iniferters (TED – tetraethylthiuram disulfide, XDT – p -xylylene bis( N , N -diethyldithiocarbamate) or BDDC – benzyl N , N -dimethyl-dithiocarbamate) were combined to hydroxyethyl methacrylate (HEMA), hydroxyethyl acrylate (HEA) or urethane dimethacrylate (UDMA), with or without a conventional UV initiator (DMPA – 2,2-dimethoxy-2-phenyl-acetophenone). Materials were photoactivated with 320–390 nm at 40 mW/cm 2 . Conversion was followed for 10 min using near-IR (6165 cm −1 , Nicolet 6700). Exposure times were adjusted to produce 20–40% conversion at the end of the illumination period. Results were submitted to two-way ANOVA/ Tukey’s test (alfa = 5%).
| Monomer | Initiator system | Exposure time (s) | DC at 10 min (%) | R P at 10% DC (% s −1 ) | DC at light off (%) |
|---|---|---|---|---|---|
| UDMA | XDT | 75 | 43.9 (5.4) ab | 0.86 (0.01) c | 30.9 (0.3) ab |
| BDDC | 153 | 36.1 (0.5) b | 0.38 (0.03) c | 29.1 (0.4) bc | |
| DMPA/TED | 5 | 33.8 (6.5) bB | 3.93 (0.71) bB | 22.4 (2.9) cB | |
| DMPA | 3 | 50.1 (1.0) aA | 7.36 (0.30) aA | 35.5 (2.7) aA | |
| HEMA | DMPA/TED | 135 | 27.4 (3.5) BC | 0.22 (0.02) C | 27.8 (1.9) BC |
| DMPA | 29 | 29.0 (2.4) BC | 0.96 (0.03) C | 26.9 (1.7) BC | |
| HEA | DMPA/TED | 480 | 22.8 (1.8) C | 0.13 (0.02) C | 23.0 (1.9) BC |
| DMPA | 2 | 32.9 (5.2) BC | 6.39 (0.79) A | 26.9 (9.9) BC | |
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