A Photoinitiation System for Conventional and Controlled Radical Polymerization at Visible and NIR Wavelengths

Abstract

We report for the first time the use of phthalocyanine compounds, in conjunction with the common solvent N-methyl-2-pyrrolidone (NMP), as a photoinitiation system for radical polymerization under various visible and near-infrared wavelengths. A library of redox-inactive metallic phthalocyanine compounds were investigated for their ability to act as photosensitizers in these new two-component photoinitiation systems, for the radical polymerization of (meth)­acrylate and (meth)­acrylamide monomers. Conventional radical polymerization under these conditions was successful, and moreover, the addition of reversible addition–fragmentation chain transfer (RAFT) agents to these systems led to the production of polymers with molecular weights in agreement with theoretical predictions and molecular weight distributions typically lower than 1.15. In contrast to our previous systems described as photoinduced electron/energy transfer–reversible addition–fragmentation chain transfer (PET-RAFT) where RAFT agent is activated by the photocatalyst, we propose that the phthalocyanine compounds react via a reductive quenching pathway to oxidize NMP to an NMP radical, which can directly initiate the polymerization of monomers.

Visible Light Induced Cationic Polymerization of Epoxides by Using Multiwalled Carbon Nanotubes

“…By applying a large variety of photoinitiaiting systems and a combination of different monomers, various complex polymer architectures, such as block and graft copolymers as well as hyperbranched polymers, can be prepared. New photochemical methodologies have recently been developed to obtain polymers with a controlled molecular weight, structure, and functionality . Photopolymerizations can be initiated in various ways, such as through radical, cationic, or even anionic processes.…”

“…New photochemical methodologies have recently been developed to obtain polymers with a controlled molecular weight, structure, and functionality. [5,6] Photopolymerizations can be initiated in various ways, such as through radical, cationic, or even anionic As cationic polymerizations can successfully be initiated by the redox process, which involves photochemically generated radicals and iodonium salts, [26] it seemed appropriate to trigger cationic polymerization epoxy using MWCNTs.…”

A Versatile Approach for In Situ Monitoring of Photoswitches and Photopolymerizations

“…To illustrate the utility of this strategy, the Φ of two photochromic small molecules, a donor–acceptor Stenhouse adduct (DASA) as well as a diarylethene (DAE), were determined from optically dense propagating fronts. Complementing the small‐molecule studies, this new technique was also used to analyze several light‐driven controlled polymerizations, leading to kinetic insights and a detailed understanding of molecular weight, structure, and dispersity evolution with conversion . These examples showcase the versatility and potential impact of our method on the broad field of photochemistry.…”

Continuous Flow Photoinduced Reversible Deactivation Radical Polymerization

“…[17,[26][27][28][95][96][97][98] Photo-RAFT with photoinitiator, RAFT without exogenous catalyst/initiator (iniferter), and photoinduced electron/energy transfer RAFT (PET-RAFT) have roused growing concern for the well-controlled features and the accelerated polymerization rates. [99] More recently, a library of photocatalysts including phthalocyanine compounds, [100] Eosin Y, [101] zinc tetraphenylporphyrin (ZnTPP) [102][103] and crude extracted chlorophyll [104] were disclosed, which could mediate the polymerizations under visible and near-infrared light even in the presence of oxygen. [103] The combination of microflow technique and photoinduced RAFT and iniferter polymerization will be discussed below.…”