Controllable polymerizations: Interactions of monomer and iniferter structure

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%).

Results

Table. Degree of conversion (DC) and rate of polymerization at 10% conversion for the experimental groups. Same superscript within the same column indicates no statistical difference at 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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Nov 30, 2017 | Posted by in Dental Materials | Comments Off on Controllable polymerizations: Interactions of monomer and iniferter structure
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