Publications : 2013

A series of new dyes based on (thio)barbituric acid derivatives were synthesized and used as photoinitiators of polymerization upon very soft irradiation (laser diodes at 457 nm and 473 nm; blue LED bulbs or even a halogen lamp). These dyes can work according to an oxidative cycle (dye/diphenyl iodonium salt/N-vinylcarbazole system) or a reductive cycle (dye/amine/alkyl halide system) and partly behave as organic photocatalysts. Ring-opening polymerization (ROP) of epoxides and radical polymerization (RP) of acrylates are easily promoted. Excellent

New Type I and Type II photoinitiators based on 2,2-dimethoxy-2-phenylacetophenone (DMPA), benzophenone (BP) and thioxanthone (TX) linked to a pyrene (Py) moiety (Py_DMPA, Py_BP, Py_TX) are proposed here for the free radical polymerization of acrylates and the cationic polymerization of epoxides and vinylethers under a Xe-Hg lamp, laser diode at 405 nm or a halogen lamp. Excellent polymerization profiles using Py_DMPA and Py_BP are obtained, i.e. better than those recorded with the reference compounds (DMPA and BP). Specifically, Py_DMPA and Py_BP absorb in the near UV-visible range (360-420 nm range; absorption red-shift similar to 15 nm), exhibit huge epsilon values (up to a 90 fold increase) and high photochemical reactivity. The mechanisms analyzed by electron spin resonance, steady state photolysis, fluorescence and laser flash photolysis experiments are discussed for the different initiating systems.

Two new photoinitiators with unprecedented light absorption properties are proposed on the basis of a suitable truxene skeleton where several

Among other photoinitiating systems, aromatic ketone based compounds have been largely exploited as photoinitiators (PIs). However, none of these compounds efficiently absorb above 420 nm. The search of novel architectures of PIs for getting an important red-shift of the absorption is crucial for the use of visible lights for polymer synthesis. Novel bifunctional dyes derived from the Michler?s ketone structure are proposed here as photoinitiators for the free radical polymerization of acrylates and the cationic polymerization of epoxides upon exposure to 457, 473, and 532 nm laser diodes and even to a green LED bulb at 514 nm. Excellent polymerization profiles are obtained. These original dyes exhibit a push?pull molecular character for a remarkable covering of the visible lights. The formation of the radicals and the ions in the two- and three-component photoinitiating systems is described and the initiation steps are discussed.