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|