NIR Photocontrolled Organotellurium-Mediated Reversible-Deactivation Radical Polymerization by Activation of C-Te Bonds with Organotellurium Radicals

The development of near-infrared (NIR) photocontrolled reversible-deactivation radical polymerization (RDRP) technology has been a pursued but challenging goal. Herein, an emerging NIR photocontrolled organotellurium-mediated radical polymerization (TERP) system different from traditional ways has been developed successfully in the absence of photocatalysts (PCs) by employing organotellurium chain transfer agents (CTAs) and ditellurium compounds (dimethyl/diphenyl ditellurium), and the activation of tellurium-containing dormant species by organotellurium radicals that are generated in situ from ditellurium is the key to this technique. This TERP strategy driven by NIR light here is exceptionally simple compared to other NIR photopolymerization technologies, containing only the monomer, organotellurium CTA, and ditellurium mediator, bypassing the conventional dependency on special NIR PCs and solvents, which also breaks with the convention that the action spectrum (emission spectra of light sources) should correspond to the main absorption spectrum of the reactants. Actually, the photodissociation of fragile bonds (C-Te and Te-Te) in tellurides may be a specific photochemical reaction; we find that the matching between bond dissociation energy (BDE) and the energy of photon may be a more reasonable photochemical protocol, and it is not always relevant to their main absorption window. Additionally, based on this protocol, well-defined polymers have been synthesized successfully under NIR irradiation (lambda = 700-1000 nm) at room temperature, and the strong penetration capability of NIR light has also been illustrated by the fact that the TERP still proceeds smoothly even with a thick barrier (A4 paper or chicken skin).