NIR Light‐Induced ATRP for Synthesis of Block Copolymers Comprising UV‐Absorbing Moieties

Abstract

NIR exposure at 790 nm activated photopolymerization of monomers comprising UV‐absorbing moieties by using [CuII/(TPMA)]Br2 (TPMA=tris(2‐pyridylmethyl)amine) in the ppm range and an alkyl bromide as initiator. Some of them comprised structural elements selected either from those showing proton transfer or photocycloaddition upon UV excitation. Polymers obtained comprise living end groups serving as macroinitiator for controlled synthesis of block copolymers with relatively narrow molecular weight distributions. Chromatographic results indicated formation of block copolymers produced by this synthetic approach. Free‐radical polymerization of monomers pursued for comparison exhibited the expected broader dispersity of molecular weight compared to photo‐ATRP. Polymerization of these monomers by UV photo‐ATRP failed on the contrary to NIR photo‐ATRP demonstrating the UV‐filter function of the monomers. This work conclusively provides a new approach for the polymerization of monomers comprising UV‐absorbing moieties through photo‐ATRP in the NIR region. This occurred in a simple and efficient pathway. However, studies also showed that not all monomers chosen successfully proceeded in the NIR photo‐ATRP protocol.

NIR‐Sensitized Cationic and Hybrid Radical/Cationic Polymerization and Crosslinking

“…New methods on photopolymerization with focus on either radical [1][2][3][4][5][6][7][8][9][10] or cationic mechanism [9,10] have received great interest within the last years. [11,12] Thebiggest growth on publications has been noticed focusing on radical polymerization where numerous reports appeared considering new approaches related to living radical polymerization [3,4,[13][14][15][16][17][18][19][20][21] applying UV, [16] visible [17] or near-infrared (NIR) [13,18] radiation following either aR AFT [3,4,[19][20][21] or ATRP [13][14][15]22,23] reaction protocol. Remarkable are those studies reporting polymerization under oxygen.…”

Developments in the Components of Metal‐Free Photoinitiated Organocatalyzed‐Atom Transfer Radical Polymerization (O‐ATRP)

“…The recent developments in the field involve incorporating carbon dots as photocatalysts, [106] and progress in surface‐initiated O‐ATRP for synthesizing polymer‐inorganic hybrid structures [107] expand the extent of the field beyond chemistry to a broader range of materials science and technology. Innovative advancement like the use of ultrasound for mediating the ATRP [108] and the recent development of a successful light‐induced ATRP in the infrared region [109] are development fields indeed defines the prevalent and propitious nature of ATRP for future innovations.…”

Distinct Sustainable Carbon Nanodots Enable Free Radical Photopolymerization, Photo‐ATRP and Photo‐CuAAC Chemistry

“…It enables the tailor‐made photoinduced synthesis at the nanoscale and brings therefore material science to some of the aforementioned applications. Therefore, questions have arisen to connect suitable initiator systems with modern light sources emitting in the UV, [28] visible [4, 27] or NIR [29, 30] range. New regulations with focus to replace older mercury light sources have accelerated these activities [31] .…”

“…They involve the in situ reduction of Cu II to generate Cu I by 1)various reducing agents, 2)photochemical processes, 3)electrochemical redox processes, and 4)copper‐comprising nanoparticles [5, 26, 43, 44] . Particularly, the in situ photolytic generation of Cu I complexes from Cu II under irradiation to initiate controlled radical polymerization facilitates CRP with a copper concentration residing at the ppm‐scale has received remarkable attention [27, 29, 30] . This level of Cu II appears as less harmful.…”