Non-isocyanate Synthesis of Covalent Adaptable Networks Based on Dynamic Hindered Urea Bonds: Sequential Polymerization and Chemical Recycling.

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.

A comparative study of remotely sensed reservoir monitoring across multiple land cover types.

Continuous monitoring of reservoirs and dams is essential for efficient water management. Synthetic Aperture Radar (SAR) imagery offers the potential for continuous monitoring of surface water through all-weather ground observation. The objective of this study is to enhance the accuracy of water body detection and water quantity estimation by applying 64 combinations of speckle filtering and object detection techniques to Sentinel-1 imagery. For speckle filtering, the Median, Gaussian, Lee, and Frost techniques were used with various window sizes (3, 5, 7, and 9). For water body detection, the Otsu, Kittler-Illingworth (KI), Chan-Vese (CV), and K-means methods were employed. The study area included three reservoirs and two dams in Korea, encompassing a variety of water surface sizes and types of land cover. To validate the accuracy of each water body detection combination, manual delineation-based water mask images from Sentinel-2 were employed. Furthermore, a regression equation (y=axb) between water surface area and storage was used to estimate water storage based on SAR imagery, followed by time-series validation using in-situ data. The research results indicate that the optimal detection technique varies significantly depending on the type of surrounding land cover and the size of the water body. The highest performance was observed for the CV technique combination for waterfront pixels, and for the KI technique combination for other land cover pixels. In speckle filtering techniques using a large window size, the false detection rate caused by vegetation and buildings was low; however, the boundaries of water bodies were blurred. Consequently, using smaller window sizes in SAR imagery and leveraging optimal water body detection combinations specific to land cover types, along with post-processing using masking data, would enhance the performance of water surface area and storage estimation.

NIR-Triggered High-Efficiency Self-Healable Protective Optical Coating for Vision Systems.

Recently, self-healing materials have evolved to recover specific functions such as electronic, magnetic, acoustic, structural or hierarchical, and biological properties. In particular, the development of self-healing protection coatings that can be applied to lens components in vision systems such as augmented reality glasses, actuators, and image and time-of-flight sensors has received intensive attention from the industry. In the present study, we designed polythiourethane dynamic networks containing a photothermal N-butyl-substituted diimmonium borate dye to demonstrate their potential applications in self-healing protection coatings for the optical components of vision systems. The optimized self-healing coating exhibited a high transmittance (∼95% in the visible-light region), tunable refractive index (up to 1.6), a moderate Abbe number (∼35), and high surface hardness (>200 MPa). When subjected to near-infrared (NIR) radiation (1064 nm), the surface temperature of the coating increased to 75 °C via the photothermal effect and self-healing of the scratched coatings occurred via a dynamic thiourethane exchange reaction. The coating was applied to a lens protector, and its self-healing performance was demonstrated. The light signal distorted by the scratched surface of the coating was perfectly restored after NIR-induced self-healing. The photoinduced self-healing process can also autonomously occur under sunlight with low energy consumption.

Discovery of High-Performing Metal-Organic Frameworks for On-Board Methane Storage and Delivery via LNG-ANG Coupling: High-Throughput Screening, Machine Learning, and Experimental Validation.

Liquefied natural gas (LNG) gasification coupled with adsorbed natural gas (ANG) charging (LNG-ANG coupling) is an emerging strategy for efficient delivery of natural gas. However, the potential of LNG-ANG to attain the advanced research projects agency-energy (ARPA-E) target for onboard methane storage has not been fully investigated. In this work, large-scale computational screening is performed for 5446 metal-organic frameworks (MOFs), and over 193 MOFs whose methane working capacities exceed the target (315 cm3 (STP) cm-3 ) are identified. Furthermore, structure-performance relationships are realized under the LNG-ANG condition using a machine learning method. Additional molecular dynamics simulations are conducted to investigate the effects of the structural changes during temperature and pressure swings, further narrowing down the materials, and two synthetic targets are identified. The synthesized DUT-23(Cu) and DUT-23(Co) show higher working capacities (≈373 cm3 (STP) cm-3 ) than that of any other porous material under ANG or LNG-ANG conditions, and excellent stability during cyclic LNG-ANG operation.

Direct C(sp3)-H Cyanation Enabled by a Highly Active Decatungstate Photocatalyst.

A highly efficient, direct C(sp3)-H cyanation was developed under mild photocatalytic conditions. The method enabled the direct cyanation of various C(sp3)-H substrates with excellent functional group tolerance. Notably, complex natural products and bioactive compounds were efficiently cyanated.

Aerobic Oxidation of Benzylic Carbons Using a Guanidine Base.

Metal-free reaction conditions featuring oxygen and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) were employed for the selective oxidation of benzyl amines and active methylene compounds to afford various amides and ketones. Owing to the strong basicity of guanidine bases, TBD is presumed to play an important role in the cleavage of the C-H bond at the benzylic position of peroxide intermediates, which were formed by the reaction with oxygen.

The Origin of p-Xylene Selectivity in a DABCO Pillar-Layered Metal-Organic Framework: A Combined Experimental and Computational Investigation.

We report high experimental p-xylene (pX) selectivity in a pillar-layered metal-organic framework, DUT-8(Cu). Vapor- and liquid-phase adsorption experiments were carried out to confirm high pX selectivity and large pX uptakes in DUT-8(Cu). Grand canonical Monte Carlo simulation results show that the presence of DABCO ligands allows for the packing of pX molecules and is responsible for the pX selective nature of the material. The simulation also suggests that the presence of isooctane solvents in the liquid-phase experiments plays an essential role by lowering the adsorption of other xylene isomers, and leads to increased pX selectivity in the liquid-phase as compared to the vapor phase. Density functional theory simulations show that the preferential arrangement is due to the preferential adsorption of pX on the DABCO ligand and the preferential adsorption of isooctane over other xylene isomers.