Covestro (Germany)

The aqueous solubility of a substance is a critical physicochemical property for designing environmental fate and toxicity tests. The hydrophobic nature and water-reactivity of aromatic diisocyanates constitute significant challenges to determining their aqueous solubility: the establishment of a steady-state equilibrium cannot readily be observed because substance composition and the dissolution process are variable and dynamic. Criteria developed in a previous publication were applied in this work to determine the solubility of 2,4’-methylene diphenyl diisocyanate (MDI) in Elendt M4 medium in the presence of 0.001% (10 μL/L) acetonitrile as a co-solvent. The value at 295 ± 2 K was 11.7 μg/L with a confidence interval of 9.9–13.6 μg/L. The availability of an experimental value for the first time allows for revision of the quantitative structure-activity relationship estimation tools, which – for lack of experimental data – currently predict solubilities (much) in excess of 1 mg/L. In addition, the low solubility enables and necessitates developing testing scenarios that are at the same time realistic compared to the potential exposure scenarios and consistent with the physical-chemical properties of methylene diphenyl diisocyanate and its derivatives.

Abstract The article contains sections titled:1Introduction2Physical Properties3Chemical Properties3.1Reaction with Nucleophiles3.2Cycloaddition Reactions4Production4.1Phosgenation of Free Amines4.2Other Phosgenation Procedures4.2.1Phosgenation of Amine Hydrochlorides4.2.2Phosgenation of Carbamate Salts4.2.3Phosgenation in the Gas Phase4.2.4Phosgenation of Ureas4.3Non‐phosgene Processes5Environmental Protection6Quality Specifications and Analysis7Storage and Transportation8Uses9Economic Aspects10Toxicology and Occupational HealthReferences

We present a new method for investigating the oxidation and emission behavior of air-permeable materials. Employing this method, a differentiated statement can be made about the extent to which critical volatile organic compounds (VOCs) such as formaldehyde, acetaldehyde, and acrolein are contained in the material as impurities or formed by thermo-oxidative degradation of the polymer matrix in the use phase. The parameters affecting methods of VOC analysis are reviewed and considered for the developed method. The molecular mechanisms of VOC formation are discussed. Toxicological implications of the reaction kinetics are put into context with international guidelines and threshold levels. This new method enables manufacturers of cellular materials not only to determine the oxidative stability of their products but also to optimize them specifically for higher durability. Environmental ImplicationCellular materials are ubiquitous in the technosphere. They play a crucial role in various microenvironments such as automotive interiors, building insulation, and cushioning. These materials are susceptible to oxidative breakdown, leading to the release of formaldehyde, acetaldehyde, and acrolein. The ecotoxicological profiles of these compounds necessitate monitoring and regulation. The absence of reproducible and reliable analytical methods restricts research and development aimed at risk assessment and mitigation. This work significantly enhances the toolbox for optimizing the oxidative stability of any open-cell cellular material and evaluating these materials in terms of their temperature-dependent oxidation and emission behavior.

Polyurethane (PU) foams are a large volume commodity product and as such pose a considerable recycling challenge for the polymer manufacturing industry. The incorporation of dynamic covalent bonds within a PU network chemistry is a possible strategy to improve the sustainable development of PU foams. Herein, we report the outcome of a research program aimed at the incorporation of thermoreversible triazolinedione (TAD)-indole linkages within an industrial standard PU foam formulation. A scalable synthesis of the required TAD–indole building blocks was developed, aiming at maximizing their physicochemical compatibility with standard polyol and isocyanate PU foam ingredients. A pilot scale synthesis of a TAD-based cross-linker was developed, affording more than 50 kg of an IPDI-derived bis-urazole building block. Propoxylation of the indole fragments proved to be a key technology enabling the kilogram scale production of TAD–indole based polyols. The innovative dynamic covalent polyols were successfully used to produce a range of flexible PU foams and elastomers in a solvent-free foam formulation. Owing to the thermoreversible nature of the TAD–indole linkers, the PU foams could be processed into PU elastomers through thermal compression molding, which could be further recycled up to 7 times in the same manner. We studied the effect of network compositions on the foaming process and on the recycling efficiency. The thermal and mechanical properties of the materials have been studied with thermal analysis, tensile measurements, and rheology. This work demonstrates that TAD–indole chemistry is a viable strategy to improve polyurethane recycling but also points out some critical aspects and obstacles related to the design of such dynamic covalent PU foams.

The German Chemical Society (GDCh) Board of Directors chose the motto "Rethinking Chemistry" last year to address challenges connected to climate change, loss of natural resources, and geopolitical conflicts as the guiding principle of all our endeavors and actions. Rethinking Chemistry indicates the Board's desire to encourage scientists to approach chemistry in a new way, with a focus on reconsidering the field from many different angles. By taking a holistic approach, the Board intends to foster innovative, sustainable, and effective ways to use chemistry. Rethinking Chemistry is also the motto of the GDCh Science Forum Chemistry (WiFo) 2023, and a Special Collection on the homepage of Angewandte Chemie is dedicated to this event and its motto. Rethinking Chemistry means something different in each area of chemistry, and the WiFo 2023 as well as this Special Collection of Angewandte Chemie showcase its many facets.

Abstract The German Chemical Society (GDCh) Board of Directors chose the motto “Rethinking Chemistry” last year to address challenges connected to climate change, loss of natural resources, and geopolitical conflicts as the guiding principle of all our endeavors and actions. Rethinking Chemistry indicates the Board's desire to encourage scientists to approach chemistry in a new way, with a focus on reconsidering the field from many different angles. By taking a holistic approach, the Board intends to foster innovative, sustainable, and effective ways to use chemistry.Rethinking Chemistry is also the motto of the GDCh Science Forum Chemistry (WiFo) 2023, and a Special Collection on the homepage of Angewandte Chemie is dedicated to this event and its motto. Rethinking Chemistry means something different in each area of chemistry, and the WiFo 2023 as well as this Special Collection of Angewandte Chemie showcase its many facets.

The ring opening polymerization of cyclic carbonates made from epoxide and CO2 to CO2-containing polymers constitutes an emerging technology of particular industrial interest. Considering the reaction of ring-opening polymerization of cyclic ethylene carbonate to produce polyethercarbonate polyols, several types of catalysts were tested experimentally and mechanistic pathways were proposed, but a detailed analysis of structure property relationship including the CO2-liberation pathways is still lacking. This contribution is using computational methods to investigate reported benchmark catalysts with the lead structure AxMyOz (A: alkali metal or alkyl, M: main group element or transition metal) that are particularly approved as effiecient catalysts for industrial purpose. Employing DFT-metadynamics simulations, free energy surfaces (FESs) for the key-steps in the catalytic polymerization of cyclic ethylene carbonate (cEC) are generated. Important structural criteria and characteristics of the catalysts that influence the catalytic performance and (side)reaction pathways are determined. It turns out that less nucleophilicity of the catalyst anion and more labile cations remain major criteria for prohibiting CO2 liberation during polymerization. The key learnings of this contribution currently serve as a basis to develop the next generation of catalysts to bring this emerging carbon capture and use (CCU) technology into industrial application.