Synthesis and Behavior of Hexamethylenetetramine-Based Ionic Liquids as an Active Ingredient in Latent Curing Formulations with Ethylene Glycol for DGEBA

Rational Design of Organic Manganese Halides for High Quantum Efficiency and Stability

Organic manganese halides have gained attention as luminescent materials due to their characteristics, such as low toxicity, ease of synthesis, and high photoluminescence quantum yield (PLQY). This study challenges the common belief that increasing the Mn-Mn distance invariably boosts PLQY. It introduces a 3D diagram illustrating the importance of ground-state and excited-state band alignments in influencing PLQY. The research identifies how different organic cations result in two distinct band alignments, thus impacting PLQY. Additionally, the research delves into the effects of temperature and pressure on the stability of three organic manganese bromides. Findings indicate that the structural attributes of organic cations significantly influence the materials' responses to thermal stress and pressure. For instance, (PPh4)2MnBr4, characterized by a strong conjugation effect and stable structure, displays superior thermal stability and pressure resistance. Conversely, (N-BHMTA)2MnBr4, with a more intricate structure and lower stability, exhibits susceptibility to irreversible structural alterations under elevated temperature and pressure. These insights are pivotal for developing stable, efficient luminescent materials across diverse applications.

Supported Ionic Liquid-Phase Materials (SILP) as a Multifunctional Group of Highly Stable Modifiers and Hardeners for Carbon and Flax Epoxy Composites

This paper introduces a novel approach to enhance epoxy resin formulations by using SILP materials as multifunctional hardeners and fillers in composite structures reinforced with carbon and flax fibers. This study explores the integration of ionic liquids (ILs) onto a silica support structure, presenting various permutations involving silica selection, ionic liquid choice, and concentration. The focus of this study was to elucidate the influence of SILP on resin curing ability and the mechanical properties of the resulting composites. Detailed research was conducted, including Brunauer-Emmett-Teller analysis (BET) for SILP materials and curing characterization for epoxy resin formulations with different SILP materials. Furthermore, the mechanical properties of the obtained composites were determined by Scanning Electron Microscopy analysis (SEM) (the force at break, the maximum elongation at break, tensile strength, and modulus of elasticity). Through SILP incorporation, the mechanical properties of composites, including the modulus of elasticity and tensile strength, are substantially improved, a phenomenon akin to traditional filler effects. The findings highlight SILP materials as prospective candidates for concurrent hardening and filling roles within composites (through a single-step procedure, with prolonged storage stability and controlled processing conditions), particularly pertinent as the composite industry veers toward epoxy bioresins necessitating liquefaction via temperature application.

Ruthenium-Induced Decomposition of Hexamethylenetetramine as a Tool for the Acid-Free Sommelet Reaction in Aqueous Medium

Hexamethylenetetramine (HMTA) is one of the most versatile and most utilized nitrogen-containing heterocyclic compounds in academia and industry. Most of the reactions involving HMTA employ stoichiometric or excess amounts of acid, which hamper the sustainability of the reactions. Herein, we report the first example of the ruthenium-mediated decomposition of HMTA at room temperature, supported by a detailed mechanistic study using thermogravimetric analysis/differential thermal analysis, variable-temperature NMR, UV-vis spectroscopy, and density functional theory techniques. The mechanism study also involves a comparison of the decomposition of HMTA, protonated HMTA, [RuCl3(HMTA)], and [FeCl3(HMTA)], which revealed that [RuCl3(HMTA)] decomposes at the lowest temperature and has the lowest HOMO-LUMO band gap of 2.66 eV. The ruthenium-induced decomposition of HMTA is successfully used as a tool to increase the sustainability of the Sommelet reaction as it employs simple RuCl3·nH2O as a catalyst in as low as 0.5 mol % concentration in aqueous medium. The developed methodology is found to be very selective and efficient even for the very challenging substrates, namely, aliphatic aldehydes and substrates with electron-withdrawing substituents. The findings of this work are the first of its kind in which ruthenium is employed in the Sommelet reaction and also provide a possible platform to improve the sustainability of all reactions involving HMTA as a reactant/reagent.