Twenty years since coming into force, the Stockholm Convention has become a \"living\" global agreement that has allowed for the addition of substances that are likely, as a result of their long-range environmental transport (LRET), to lead to significant adverse effects. The recent listing of the phenolic benzotriazole UV-328 in Annex A and a draft nomination of three cyclic volatile methylsiloxanes (cVMS) for Annex B draw attention to the fact that many chemicals are subject to LRET and that this can lead to questionable nominations. The nomination of UV-328 and the draft nomination of cVMS also raise the spectre of regrettable substitutions. At the same time, atmospheric monitoring across the globe reveals that environmental releases of several unintentionally produced POPs listed in Annex C, such as hexachlorobenzene and hexachlorobutadiene, are continuing unabated, highlighting shortcomings in the enforcement of the minimum measures required under Article 5. There is also no evidence of efforts to substitute a chemical whose use has been known for three decades to unintentionally produce polychlorinated biphenyls. These developments need to be rectified to safeguard the long-term viability and acceptance of a global treaty of undeniable importance.

HypothesisFoaming in diesel fuels is not well understood and leads to operational challenges. To combat deleterious effects of foaming, diesel formulations can include additives called antifoams. Existing antifoams, unfortunately, are inherently ash-generating when combusted, with unknown environmental impacts. They are prohibited in certain countries, so identifying effective alternative ash-free antifoam chemistries is needed. ExperimentsWe conduct systematic characterization of foam stabilization and antifoaming mechanisms in diesel for two different antifoams (silicone-containing & ashless chemistries). Employing a custom technique combining single-bubble/single-antifoam-droplet manipulation with white light interferometry, we also obtain mechanistic insights into foam stability and antifoam dynamics. ResultsCoalescence times from both bulk foam and single bubble experiments confirm ashless antifoams are effective at reducing foaming, demonstrating the potential of ashless antifoams. Further, we perform single-antifoam-droplet experiments and obtain direct experimental evidence revealing the elusive antifoaming mechanisms. Interestingly, the silicone-containing and ashless antifoams seemingly function via two different mechanisms: spreading and dewetting respectively. This surprising finding refutes conventional wisdom that spreading is likely the only antifoam mechanism in diesels. These results and the reported experimental framework significantly enhance the scientific understanding of non-aqueous foams and will accelerate the engineering of alternative antifoam chemistries for non-aqueous systems.

In the presented study, the effectiveness of a siloxane polyether (HOL7) coating on glass against microbiological colonization was assessed using microalgae as a key component of widespread aerial biofilms. The siloxane polyether was successfully synthesized by a hydrosilylation reaction in the presence of Karstedt\'s catalyst. The product structure was confirmed by NMR spectroscopy and GPC analysis. In addition, the thermal stability of HOL7 was studied by thermogravimetric measurement. Subsequently, the surfaces of glass plates were modified with the obtained organosilicon derivative. In the next step, a microalgal experiment was conducted. A mixture of four strains of algal taxa isolated from building materials was used for the experiment-Chlorodium saccharophilum PNK010, Klebsormidium flaccidum PNK013, Pseudostichococcus monallantoides PNK037, and Trebouxia aggregata PNK080. The choice of these algae followed from their wide occurrence in terrestrial environments. Application of an organofunctional siloxane compound on the glass reduced, more or less effectively, the photosynthetic activity of algal cells, depending on the concentration of the compound. Since the structure of the compound was not based on biocide-active agents, its effectiveness was associated with a reduction in water content in the cells.

Direct observation by the naked eye of fluorescence-stained microbes adsorbed on surface imprinted polymers (SIPs) is highly challenging and limited by speed, accuracy and the semiquantitative nature of the method. In this study, we tested for the presence of spores of Fusarium oxysporum f. sp. cubense race 4 (Foc4), which cause severe banana Fusarium wilt disease and reduces the area of banana plants. This kind of spore can become dormant in soil, which means that the detection of secreted molecules (molecular imprinting) in soil may be inaccurate; detection methods such as polymerase chain reaction (PCR) and Raman spectroscopy are more accurate but time-consuming and inconvenient. Therefore, a semiquantitative and rapid SIP detection method for Foc4 was proposed. Based on the ITO conductive layer, a reusable and naked-eye-detectable Foc4-PDMS SIP film was prepared with a site density of approximately 9000 mm-2. Adsorption experiments showed that when the Foc4 spore concentration was between 104 to 107 CFU/mL, the number of Foc4 spores adsorbed and the fluorescence intensity were strongly correlated with the concentration and could be fully distinguished by the naked eye after fluorescence staining. Adsorption tests on other microbes showed that the SIP film completely recognized only the Foc series. All the results were highly consistent with the naked-eye observations after fluorescence staining, and the results of the Foc4-infected soil experiment were also close to the ideal situation. Taken together, these results showed that Foc4-PDMS SIPs have the ability to rapidly and semiquantitatively detect the concentration of Foc in soil, which can provide good support for banana cultivation. This method also has potential applications in the detection of other fungal diseases.

The removal of volatile methyl siloxanes (VMS) from landfill biogas is crucial for clean energy utilization. VMS are usually found together with aromatic compounds in landfill biogas of which toluene is the major representative. In the present study, two biofilters (BFs) packed with either woodchips and compost (WC) or perlite (PER) were used to study the (co-) removal of octamethyltrisiloxane (L3) and octamethylcyclotetrasiloxane (D4) from gas in presence and absence of toluene, used as a representative aromatic compound. The presence of low inlet toluene concentrations (315 ± 19 - 635 ± 80 mg toluene m-3) enhanced the VMS elimination capacity (EC) in both BFs by a factor of 1.8 to 12.6. The highest removal efficiencies for D4 (57.1 ± 1.1 %; EC = 0.12 ± 0.01 gD4 m-3 h-1) and L3 (52.0 ± 0.6 %; EC = 0.23 ± 0.01 gL3 m-3 h-1) were observed in the BF packed with WC. The first section of the BFs (EBRT = 9 min), where toluene was (almost) completely removed, accounted for the majority (87.7 ± 0.6 %) of the total VMS removal. Microbial analysis revealed the impact of VMS and toluene in the activated sludge, showing a clear selection for certain genera in samples influenced by VMS in the presence (X2) or absence (X1) of toluene, such as Pseudomonas (X1 = 0.91 and X2 = 12.0 %), Sphingobium (X1 = 0.09 and X2 = 4.04 %), Rhodococcus (X1 = 0.42 and X2 = 3.91 %), and Bacillus (X1 = 7.15 and X2 = 3.84 %). The significant maximum EC values obtained by the BFs (0.58 gVMS m-3 h-1) hold notable significance in a combined system framework as they could enhance the longevity of traditional physicochemical methods to remove VMS like activated carbon in diverse environmental scenarios.

The water-rich nature of the dentin bonding microenvironment, coupled with the stresses on the bonding interface, contributes to the hydrolytic degradation of the hybrid layer, resulting in a decline in bonding durability and, ultimately, restoration failure. Currently, the 3-step etch-and-rinse technique remains the gold standard for dentin bonding, and the bonding mechanism mainly involves a physical interaction with little chemical bonding. In this study, we have developed a siloxane-modified polyurethane monomer (SPU) with acrylate and siloxane modifications that chemically binds to both collagen and hydroxyapatite in dentin. Formulated as a bisphenol A-glycidyl methacrylate alternative, the SPU monomer-based adhesive was designed to improve dentin bonding quality and durability. Attenuated total reflection Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscope, and hydroxyproline release assays were performed on SPU-treated collagen, hydroxyapatite, and acid-etched dentin slices to dentin. The physicochemical properties of the configured SPU adhesives were profiled for polymerization behavior, water contact angle, and tensile strain and strength. The bonding effectiveness was assessed through micro-tensile strength, nano-leakage tests conducted on the bonded samples before and after thermal cycle aging. Finally, we further conducted in vivo and in vitro experiments to assess the biocompatibility of adhesives. The results showed that the siloxane groups of SPU monomer could covalently bind to dentin collagen and hydroxyapatite. The incorporation of SPU in the adhesive led to a significant increase in adhesive polymerization (P < 0.05) and tensile strain at break up to 134.11%. Furthermore, the SPU adhesive significantly improved dentin bond strength (P < 0.05), reduced interfacial nano-leakage (P < 0.05), and displayed good biocompatibility. In conclusion, the application of SPU, which achieves dual chemical bonding with dentin, can improve the quality of the hybrid layer, buffer the interfacial stresses, enhance the interfacial resistance to hydrolysis, and provide a feasible strategy to extend the service life of adhesive restorations.

With octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) being considered for evaluation under the UN Stockholm Convention on Persistent Organic Pollutants, which specifically acknowledges risks of biomagnification of persistent organic pollutants in traditional foods, a study into the mechanism of the biomagnification process of D4 and D5 in Rainbow trout was conducted by combining the absorption-distribution-metabolism-excretion for bioaccumulation (ADME-B) approach to determine intestinal and somatic biotransformation rates and radiochemical analyses to identify metabolite formation. High rates of intestinal biotransformation of D4 and D5 (i.e., 2.1 (0.70 SE) and 0.88 (0.67 SE) day-1, respectively) and metabolite formation [i.e., 52.0 (17 SD)% of D4 and 56.5% (8.2 SD)% of D5 were metabolized] were observed that caused low dietary uptake efficiencies of D4 and D5 in fish of 15.5 (2.9 SE)% and 21.0 (6.5 SE)% and biomagnification factors of 0.44 (0.08 SE) for D4 and 0.78 (0.24 SE) kg-lipid·kg-lipid-1 for D5. Bioaccumulation profiles indicated little effect of growth dilution on the bioaccumulation of D4 and D5 in fish and were substantially different from those of PCB153. The study highlights the importance of intestinal biotransformation in negating biomagnification of substances in organisms and explains differences between laboratory tests and field observations of bioaccumulation of D4 and D5.

Simulated landfill bioreactors were established and operated for 635 days to investigate the dynamic release of seven siloxanes in landfill biogas (denoted by octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6)). In total, 259.45, 252.73, 233.30, 80.40, 4.35, 1.67 and 1.10 mg of D5, D3, D4, D6, L4, L5 and L3 were discharged from 57 kg of municipal solid waste (MSW). More than 70 % of the siloxanes were released before day 119, indicating that the peak period of siloxane discharge occurred during the hydrolysis and acid production stage. The cyclosiloxanes (D3, D4, D5 and D6) were the dominant siloxane species in the biogas. The mass load of discharged cyclosiloxanes was more than 98 % of that of the total siloxanes. In addition to the variation in the concentration distribution profiles of the different siloxane species in the MSW, transformations among species may have an important effect on the release of siloxanes. The main transformation products were D3 and D4 with high release rates (>20 %) and high measured contents of trimethylsilanol (TMSOH) and functional microorganisms (Pseudomonas) were observed during landfilling. These results suggested that MSW degradation and transformation of siloxanes both drive the dynamic release of siloxanes during long-term landfilling.

Herein, we report the functionalization of polyhedral oligosilsesquioxanes (POSS) and related siloxanes with arynes. Using o-triazenylarylboronic acids as aryne precursors and silica gel as the activator, the transformation of siloxane bearing various arynophilic moieties on the side chains was achieved with high yields without touching the siloxane core. This method was applied to the conjugation of POSS and pharmaceutical cores using an aryne derived from the synthetic intermediate of cabozantinib. Furthermore, orthogonal dual functionalization of POSS was realized by combining the aryne reaction with Huisgen cyclization.