Highly Efficient Near-Infrared Photoinduced Electron/Energy Transfer-Reversible Addition–Fragmentation Chain Transfer Polymerization via the Energy Transfer Upconversion Mechanism

Abstract

Near-infrared (NIR) light-mediated polymerization has been of particular interest owing to the deep penetration into opaque materials, giving rise to great potential for biomedical applications and solar photochemistry. Photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization presented unprecedented spatiotemporal control over the controlled radical polymerization process. Herein, we greatly extended the NIR region up to 980 nm by introducing rationally designed upconversion nanocrystals with low toxicity and resistance to photobleaching into PET-RAFT polymerization. Well-defined polymers with predictable molecular weight and narrow dispersity were prepared within a few hours by 980 nm NIR light-regulated PET-RAFT polymerization via the energy transfer upconversion mechanism. The livingness feature of this photopolymerization was confirmed by polymerization kinetics, chain extension experiments, and multiple controlled “on–off” light switching cycles. Furthermore, the polymerizations could be successfully performed using different monomers, in the presence of several visible light-proof barriers (i.e., pork/chicken skin) and even under aerobic conditions, demonstrating the multifold advantages of our approach.

Exploiting Reusable Edge‐Functionalized Metal‐Free Polyphthalocyanine Networks for Efficient Polymer Synthesis at Near Infrared Wavelengths

“…It is conceivable that the discrepancy observed between M n,GPC and M n,th in all cases could be attributed to the difference in hydrodynamic volume between PMA and poly(methyl methacrylate) (PMMA) standards. The comparison of different photocatalysts mediated PET‐RAFT polymerization under NIR light irradiation is summarized in Table 1 [12–24] . To the best of our knowledge, this work develops the metal‐free conjugated networks for the first time as photocatalysts for PET‐RAFT polymerization, with fast kinetics ( k ap =0.39 h −1 ) and control over molecular weight distribution (Đ=1.06–1.15) under 850 nm NIR light irradiation.…”

“…More importantly, a deeper penetration through translucent materials could be realized when longer wavelengths are employed. [12][13][14][15][16][17][18][19][20][21][22][23][24] For example, Boyer, Shanmugum and coworkers pioneered the development of bacteriochlorophyll � as a photocatalyst for the first NIR mediated RDRP system. [12] More recently, they disclosed the use of aluminum naphthalocyanine as a photosensitizer for peroxides to initiate RAFT polymerization under far-red and NIR irradiation.…”

“…In addition, high energy UV excitation can be deleterious and induces side reaction, for instance, self‐initiation of monomers and degradation of compounds, hence long wavelengths are usually preferable. More importantly, a deeper penetration through translucent materials could be realized when longer wavelengths are employed [12–24] . For example, Boyer, Shanmugum and co‐workers pioneered the development of bacteriochlorophyll ɑ as a photocatalyst for the first NIR mediated RDRP system [12] .…”

Photocatalytic Metal‐Free Radical Hydrosilylation for Polymer Functionalization†

“…Photocatalysis has attracted great attention where the light is abundant, mild, cheap, environmentally friendly, and capable of spatiotemporal control. [ 21‐26 ] In recent years, the focus has been placed on adapting photocatalytic reactions in polymer synthesis, such as post‐modification or polymerization, [ 22,27‐30 ] and the organic reaction needs to be highly reactive and efficient due to the reduced mobility of active species in the polymer chains. [ 22 ] Therefore, some efficient photo‐induced reactions have been used to post‐modify polymers.…”

Exploiting Reusable Edge‐Functionalized Metal‐Free Polyphthalocyanine Networks for Efficient Polymer Synthesis at Near Infrared Wavelengths

“…In addition, high energy UV excitation can be deleterious and induces side reaction, for instance, self‐initiation of monomers and degradation of compounds, hence long wavelengths are usually preferable. More importantly, a deeper penetration through translucent materials could be realized when longer wavelengths are employed [12–24] . For example, Boyer, Shanmugum and co‐workers pioneered the development of bacteriochlorophyll ɑ as a photocatalyst for the first NIR mediated RDRP system [12] .…”