Localized Surface Plasmon Resonance Meets Controlled/Living Radical Polymerization: An Adaptable Strategy for Broadband Light‐Regulated Macromolecular Synthesis

Near-Infrared Light-Induced Reversible Deactivation Radical Polymerization: Expanding Frontiers in Photopolymerization

Photoinduced reversible deactivation radical polymerization (photo-RDRP) or photoinduced controlled/living radical polymerization has emerged as a versatile and powerful technique for preparing functional and advanced polymer materials under mild conditions by harnessing light energy. While UV and visible light (λ = 400-700 nm) are extensively employed in photo-RDRP, the utilization of near-infrared (NIR) wavelengths (λ = 700-2500 nm) beyond the visible region remains relatively unexplored. NIR light possesses unique properties, including enhanced light penetration, reduced light scattering, and low biomolecule absorption, thereby providing opportunities for applying photo-RDRP in the fields of manufacturing and medicine. This comprehensive review categorizes all known NIR light-induced RDRP (NIR-RDRP) systems into four mechanism-based types: mediation by upconversion nanoparticles, mediation by photocatalysts, photothermal conversion, and two-photon absorption. The distinct photoinitiation pathways associated with each mechanism are discussed. Furthermore, this review highlights the diverse applications of NIR-RDRP reported to date, including 3D printing, polymer brush fabrication, drug delivery, nanoparticle synthesis, and hydrogel formation. By presenting these applications, the review underscores the exceptional capabilities of NIR-RDRP and offers guidance for developing high-performance and versatile photopolymerization systems. Exploiting the unique properties of NIR light unlocks new opportunities for synthesizing functional and advanced polymer materials.

Selective Photoactivation of Trithiocarbonates Mediated by Metal Naphthalocyanines and Overcoming Activation Barriers Using Thermal Energy

Metal naphthalocyanines (MNcs) were demonstrated to be efficient photocatalysts to activate photoinduced electron-transfer reversible addition-fragmentation chain transfer (PET-RAFT) polymerization, enabling well-controlled polymerization of (meth)acrylates under near-infrared (λ = 780 nm) light. Owing to their lower redox potential compared to previously explored photocatalysts, the activation of trithiocarbonate RAFT agents exhibited a unique selectivity that was dependent on the nature of the R group. Specifically, MNcs were capable in activating tertiary R group trithiocarbonates, whereas no activation of the trithiocarbonate possessing a secondary R group was observed. The combination of density functional theory calculations and experimental studies have revealed new mechanistic insights into the factors governing a PET-RAFT mechanism and explained this unique selectivity of MNcs toward tertiary carbon trithiocarbonates. Interestingly, by increasing the reaction temperature moderately (i.e., ∼15 °C), the energy barrier prohibiting the photoactivation of the trithiocarbonate with a secondary R group was overcome, enabling their successful activation.

Aggregation of Gold Nanoparticles Triggered by Hydrogen Peroxide-Initiated Chemiluminescence for Activated Tumor Theranostics

Developing endogenous photo-activated theranostic platforms to overcome the limitation of low tissue-penetration from external light sources is highly significant for cancer diagnosis and treatment. We report a H₂ O₂ -initiated chemiluminescence (CL)-triggered nanoparticle aggregation strategy to activate theranostic functions of gold nanoparticles (AuNPs) for effective tumor imaging and therapy. Two types of AuNPs (tAuNP & mAuNP) were designed and fabricated by conjugating 2,5-diphenyltetrazole and methacrylic acid onto the surface of AuNPs, respectively. Luminol was adsorbed onto the mAuNPs to afford self-illuminating mAuNP/Lu NPs that could produce strong CL by reaction with H₂ O₂ in the tumor microenvironment, which triggers significant aggregation of AuNPs resulting in enhanced accumulation and retention of AuNPs for activated photoacoustic imaging and photothermal therapy of tumors. We thus believe that this approach may offer a promising tool for effective tumor treatment.

Heterogeneous photocatalytic reversible deactivation radical polymerization

Photocatalytic reversible deactivation radical polymerization (RDRP) permits the use of sustainable solar light for spatiotemporal regulation of radical polymerization under mild conditions.

Polymer Nanofibers Exhibiting Remarkable Activity in Driving the Living Polymerization under Visible Light and Reusability

Visible light-driving syntheses have emerged as a powerful tool for organic synthesis and for the preparation of macromolecules under mild and environmentally benign conditions. However, precious but nonreusable photosensitizers or photocatalysts are often required to activate the reaction, limiting its practicality. Here, it is reported that poly(1,4-diphenylbutadiyne) (PDPB) nanofibers exhibit remarkable activity in driving the living free radical polymerization under visible light. Moreover, PDPB nanofibers are very stable under irradiation of visible light and can be reused without appreciable loss of activity even after repeated cycling. The nanofiber will be a promising photocatalyst with excellent reusability and stability for the reactions driven by visible light.

Nano-MOF@defected film C3N4 Z-scheme composite for visible-light photocatalytic nitrogen fixation

Photocatalytic nitrogen fixation has attracted extensive attention in recent years.

Effective Utilization of NIR Wavelengths for Photo-Controlled Polymerization: Penetration Through Thick Barriers and Parallel Solar Syntheses

This contribution details an efficient and controlled photopolymerization regulated by far-red (λ=680 nm) and NIR (λ=780 and 850 nm) light in the presence of aluminium phthalocyanine and aluminium naphthalocyanine. Initiating radicals are generated by photosensitization of peroxides affording an effective strategy that provides controlled polymerization of a variety of monomers with excellent living characteristics. Critically, long wavelength irradiation provides penetration through thick barriers, affording unprecedented rates of controlled polymerization that can open new and exciting applications. Furthermore, a more optimized approach to performing solar syntheses is presented. By combining the narrow Q-bands of these photocatalysts with others possessing complementary absorptions, layered, independent polymerizations and organic transformations may be performed in parallel under a single broadband emission source, such as sunlight.