Ji-Eun Jeong

Multifunctional near‐infrared (NIR)‐responsive materials are essential for advanced anti‐counterfeiting (ACF). Here, we present a highly transparent squarylium (SQ) dye that integrates triple NIR responses—absorption, fluorescence, and photothermal conversion—within a single molecular system. The 2,3‑dihydroperimidine structure enables strong NIR absorption (811–823 nm) and fluorescence (834–857 nm) with > 97% visible transparency (0.1 wt.%) and thermal stability (T _d = 208°C). The dye exhibits ∼13‐fold higher photostability than indocyanine green (ICG) and repeatable photothermal response under 808 nm irradiation. Screen‐printed NIR‐emitting inks on diverse substrates (films, textiles, glass, plastic bottles) show washing/solvent durability and enable QR code authentication under 832 nm excitation, maintaining no visible contrast under daylight. This work establishes a transparent single‐component NIR photonic platform for multimodal, instrument‐assisted authentication of visually imperceptible security patterns through orthogonal optical readout modes.

For decades, poly(urethane-urea) (PUU) foam production has relied on hazardous isocyanates and a complex array of external catalysts and blowing agents, resulting in chemically persistent materials that defy recycling. Herein, we break this convention by reporting the first-ever synthesis of high-performance PUU foams through an entirely autonomous, isocyanate-free, and additive-free pathway. By leveraging the ring-opening of thiazolidin-2-one with multifunctional amines, we establish a streamlined reaction that simultaneously constructs a covalent adaptable network (CAN) and triggers in situ CO2 evolution. This chemistry bypasses traditional reagents; instead, internal thiol groups react with ethylene carbonate to drive foaming under entirely catalyst-free conditions. By precisely tuning the tris(2-aminoethyl)amine ratio, we synchronize gas expansion with matrix vitrification, overcoming the structural collapse typical of nontraditional systems. The resulting foams feature hindered urea linkages that impart dissociative CAN behavior, enabling full chemical reprocessability and structural recovery over multiple cycles without compromising mechanical integrity. With an open-cell architecture and acoustic performance comparable to those of the tested commercial reference materials under the present measurement conditions, this work provides a promising strategy for designing circular cellular materials that contribute to a zero-waste chemical economy.

Commercial polyester products and technical textiles, densely embedded with high-performance Vat pigments, pose a significant environmental challenge due to the extreme difficulty of separating dyes from the polymer matrix. Traditional chemical recycling involves energy-intensive decolorization, treating these embedded pigments as problematic contaminants. In this study, we demonstrate a paradigm-shifting, "self-catalytic" upcycling strategy that bypasses dye removal by redefining the intrinsic Vat Brown 72 pigment as a built-in, high-efficiency photothermal catalyst for PET depolymerization. Exhibiting an exceptional photothermal conversion efficiency of 57.2%, these intrinsic pigment centers generate intense localized interfacial thermal hotspots under solar irradiation. Guided by real-time kinetic tracking via a selective fluorescence Fenton-EEM strategy, complete PET conversion (100%) and a 95% recovery of high-purity terephthalic acid (TPA) were achieved within just 20 minutes at a remarkably mild bulk temperature of 80 °C. The pigment catalyst exhibited robust operational durability, maintaining a high conversion rate of over 94% across five consecutive cycles, and its practical feasibility was further validated through a successful self-sustained outdoor solar demonstration. Ultimately, this work offers a highly streamlined, catalyst-free framework for the circular economy of colored technical textiles by transforming an inevitable product component into a functional processing asset.

Thermosets possess exceptional thermochemical stability and mechanical performance, but their irreversible crosslinked structures render them unrecyclable, posing severe environmental concerns. Although dynamic adaptable networks, including coordination-adaptable networks (CooANs), have emerged as sustainable alternatives, most rely on network rearrangement rather than true monomer recovery. Here, we develop a CooAN by integrating ring-opening metathesis polymerization of a vicinal-diol-functionalized cyclohexene monomer with dynamic Fe(III)–diol coordination. The resulting network enables mechanical reprocessing through reversible metal–ligand exchange and complete chemical recycling via ring-closing metathesis depolymerization of cyclohexene backbone, achieving 79% monomer recovery. The material exhibits high tensile strength (> 25 MPa), large elongation (> 600%), and distinct shape-memory behavior. It can also be extended to form conductive composites while retaining full recyclability. Precisely tuned ring-strain energy facilitates efficient depolymerization under mild conditions. This work establishes a sustainable molecular design strategy for fully recyclable thermosets that unite mechanical robustness, functional adaptability, and closed-loop chemical circularity.

The development of environmentally sustainable processes for polymer recycling is of paramount importance in the polymer industry. In particular, the implementation of chemical recycling for thermoset polymers via covalent adaptable networks (CANs), particularly those based on the dynamic hindered urea bond (HUB), has garnered intensive attention from both the academic and industrial sectors. This interest stems from its straightforward chemical structure and reaction mechanism, which are well‐suited for commercial polyurethane and polyurea applications. However, a substantial drawback of these CANs is the requisite use of toxic isocyanate curing agents for their synthesis. Herein, we propose a new HUB synthesis pathway involving thiazolidin‐2‐one and a hindered amine. This ring‐opening reaction facilitates the isocyanate‐free formation of a HUB and enables sequential reactions with acrylate and epoxide monomers via thiol–Michael and thiol–epoxy click chemistry. The CANs synthesized using this methodology exhibit superior reprocessability, chemical recyclability, and reutilizability, facilitated by specific catalytic and solvent conditions, through the reversible HUB, thiol–Michael addition, and transesterification processes.

The development of environmentally sustainable processes for polymer recycling is of paramount importance in the polymer industry. In particular, the implementation of chemical recycling for thermoset polymers via covalent adaptable networks (CANs), particularly those based on the dynamic hindered urea bond (HUB), has garnered intensive attention from both the academic and industrial sectors. This interest stems from its straightforward chemical structure and reaction mechanism, which are well‐suited for commercial polyurethane and polyurea applications. However, a substantial drawback of these CANs is the requisite use of toxic isocyanate curing agents for their synthesis. Herein, we propose a new HUB synthesis pathway involving thiazolidin‐2‐one and a hindered amine. This ring‐opening reaction facilitates the isocyanate‐free formation of a HUB and enables sequential reactions with acrylate and epoxide monomers via thiol–Michael and thiol–epoxy click chemistry. The CANs synthesized using this methodology exhibit superior reprocessability, chemical recyclability, and reutilizability, facilitated by specific catalytic and solvent conditions, through the reversible HUB, thiol–Michael addition, and transesterification processes.