Near‐Infrared Free‐Radical and Free‐Radical‐Promoted Cationic Photopolymerizations by In‐Source Lighting Using Upconverting Glass

Abstract

Am ethod is presented for the initiation of freeradical and free-radical-promoted cationic photopolymerizations by in-source lighting in the near-infrared (NIR) region using upconverting glass (UCG). This approach utilizes laser irradiation of UCG at 975 nm in the presence of fluorescein (FL) and pentamethyldiethylene triamine (PMDETA). FL excited by light emitted from the UCG undergoes electron-transfer reactions with PMDETAt of orm free radicals capable of initiating polymerization of methyl methacrylate.T oe xecute the corresponding free-radical-promoted cationic polymerization of cyclohexene oxide,i sobutyl vinyl ether,and N-vinyl carbazole,itwas necessary to use FL, dimethyl aniline (DMA), and diphenyliodonium hexafluorophosphate as sensitizer,c oinitiator,a nd oxidant, respectively. Iodonium ions promptly oxidize DMA radicals formed to the corresponding cations.T hus,c ationic polymerization with efficiency comparable to the conventional irradiation source was achieved.

Hyperbranched Polymers by Light‐Induced Self‐Condensing Vinyl Polymerization

“…Light is also used in polymerization reactions following different mechanisms including radical, cationic, anionic, and step‐growth polymerization routes. In recent years, light‐induced processes are also successfully employed in controlled/living polymerization and click reactions for the formation of various complex macromolecular architectures …”

“…[18] Light is also used in polymerization reactions following different mechanisms including radical, [19] cationic, [20][21][22] anionic, [23] and stepgrowth polymerization [24] routes. In recent years, light induced processes are also successfully employed in controlled/ living polymerization [25,26] and click reactions [27] for the forma tion of various complex macromolecular architectures. [28,29] In this review, we will focus on the recent progress in the synthesis of HBPs by using photochemical methods.…”

Exploiting the upconversion luminescence, Lewis acid catalytic and photothermal properties of lanthanide-based nanomaterials for chemical and polymerization reactions

“…Kocaarslan et al performed free-radical polymerisation of poly (methyl methacrylate) (PMMA) using a tungsten-tellurite glass doped with Yb 3+ and Tm 3+ ions (UCG) as an internal light source. 85 The upconverted photons emitted from the UCG upon NIR light irradiation (975 nm) were used to excite a fluorescein photoinitiator (FL)/pentamethyldiethylene triamine coinitiator system. In addition, free radical-promoted cationic polymerization of oxirane, cyclohexene oxide, isobutyl vinyl ether and N-vinyl carbazole was also performed by first generating a-amino radicals from a FL dye/dimethyl aniline coinitiator system, subsequently oxidized by diphenyl iodonium hexafluorophosphate (Ph 2 I + PF 6 À )…”

In Situ Ultraviolet Polymerization Using Upconversion Nanoparticles: Nanocomposite Structures Patterned by Near Infrared Light

“…The decrease in transparency of the polymeric nanocomposite is especially manifested in the UV range which provide limited depth of the UV-induced photopolymerization of the polymeric nanocomposite materials. On the other hand, most used photopolymerization techniques involve high intensity UV light in the range of ~250–350 nm, which is known to be harmful to living cells and organisms [ 28 , 29 ], rendering them as hazardous to workers in manufacturing industries and making incompatible with many biomedical applications [ 30 , 31 ]. The development of photopolymerization approaches that utilize more biocompatible and deeper penetrating near infrared (NIR) light promises to overcome hurdles associated with UV polymerization.…”

“…Another approach used to achieve NIR-sensitive photopolymerization is based on upconversion of NIR to UV light in lanthanide ions (e.g., Yb 3+ and Tm 3+ ) doped into glasses [ 31 ] or NPs [ 33 , 34 , 35 ]. Upconversion nanoparticles (UCNPs) based on a NaYF 4 :Yb 3+ ,Tm 3+ nanocrystalline core convert incident NIR light into UV or visible luminescence emissions, which, in turn, can trigger chemical reactions, including photolysis, photoisomerization, photo-coupling and photopolymerization.…”