Metal-free atom transfer radical polymerization with ppm catalyst loading under sunlight

Abstract

Organocatalytic atom transfer radical polymerization (O-ATRP) is recently emerging as an appealing method for the synthesis of metal-free polymer materials with well-defined microstructures and architectures. However, the development of highly effective catalysts that can be employed at a practical low loading are still a challenging task. Herein, we introduce a catalyst design logic based on heteroatom-doping of polycyclic arenes, which leads to the discovery of oxygen-doped anthanthrene (ODA) as highly effective organic photoredox catalysts for O-ATRP. In comparison with known organocatalysts, ODAs feature strong visible-light absorption together with high molar extinction coefficient (ε455nm up to 23,950 M–1 cm–1), which allow for the establishment of a controlled polymerization under sunlight at low ppm levels of catalyst loading.

Playing construction with the monomer toy box for the synthesis of multi‐stimuli responsive copolymers by reversible deactivation radical polymerization protocols

“…Since recovery of metal complex catalysts has been a concern with ATRP, research has been directed toward different ATRP variants that allow to minimize the concentration of metal complex catalyst and to apply mild initiation conditions 48,49,70 . Furthermore, recent investigations focus on the development of organic photocatalysts to be used in metal‐free ATRP 71 . The following examples confirm the functional group tolerance of ATRP and related polymerization protocols.…”

Metal‐Free Organocatalyzed Atom Transfer Radical Polymerization: Synthesis, Applications, and Future Perspectives

“…Interestingly, oxygen‐doped anthanthrenes are a rare example of non‐ N ‐heterocyclic organocatalysts that do not exhibit a CT character yet can controllably mediate O‐ATRP. [ 54 ]…”

Visible Light-Controlled Living Cationic Polymerization of Methoxystyrene

“…As stated in the Introduction, it is nontrivial and costly to remove residual photocatalysts of photoinduced polymerization, which impose color contamination 14 and polymer degradation 35,36 of the resulting polymers. By virtue of the Lewis acid-nature of our OPC 1, we reasoned that it could be simultaneously decolored and deactivated by simple addition of a base after the reaction.…”

“…[1][2][3][4][5] Among these stimuli, the use of light source is very attractive because of its great capacity on spatio-temporal control of the polymerization process, apart from the control of polymer chain length, narrow dispersity endowed by their living feature. For example, pioneered by Hawker and co-workers, 6,7 photo-induced atom transfer radical polymerization (photo-ATRP) has been quickly developed in the last few years, which employs a variety of photocatalysts including Ir(ppy)3, 6 perylene, 8 10-methylphenothiazine, 9 N-aryl phenothiazine, 10 N,N-diaryl dihydrophenazine, 11 Naryl phenoxazine, 12 dimethyl dihydroacridines, 13 oxygen-doped anthanthrene, 14 and other organic photocatalysts (OPCs) with complex structures. [15][16][17] Boyer and co-workers designed visible photoinduced electron transfer reversible addition fragmentation chain transfer (PET-RAFT) polymerizations with various photocatalysts and thiocarbonylthio compounds as chain transfer agent (CTA), which showed excellent on-off switching of the living polymerization.…”

“…[33][34] Furthermore, the reported photo-induced living polymerization systems generally suffer from the problems brought by residual photocatalysts. These residual photocatalysts trapped in the polymer matrix can cause color contamination 14 or heavy metal toxicity if the catalysts are metal ion-loaded, which greatly limit the potential applications of these polymers in fields including advanced photoelectronic materials and biomaterials. 35,36 In addition, they will induce polymer degradation and side reactions due to strong oxidization of excited state photocatalysts under light.…”