Cationic Mechanism Research Articles

Influence mechanism of Fe(II/III) doping on the adsorption of methylamine salts on kaolinite surfaces elucidated through DFT calculations

To investigate the effect of Fe(II/III) doping on the microscopic mechanism of methylamine salt hydrophobic modifiers on kaolinite surfaces, the adsorption characteristics of various methylamine cations on Fe(II/III)-doped kaolinite (denoted as Fe(II/III)-Kao) surfaces are calculated by density functional theory (DFT). The simulation results, including the Fukui index, adsorption energy, Mulliken bond populations, and charge analysis, reveal that Fe(II/III) doping enhances the surface activity of kaolinite, with significant effects observed in proximity to the doping site. Consequently, Fe(II/III) doping strengthens the interaction between methylamine cations and kaolinite surfaces. The adsorption mechanism of various methylamine cations on Fe(II/III)-Kao surfaces is attributed to a combination of hydrogen bonding and electrostatic attraction, with electrostatic attraction dominating the adsorption process. By comparing the adsorption energy of methylamine cations and alkyl carbon chains on Fe(II/III)-Kao surfaces, it becomes evident that the alkyl carbon chain has minimal impact on the adsorption of the hydrophobic modifier on Fe(II/III)-Kao surfaces. This finding confirms that the ammonium salt hydrophobic modifier primarily adsorbs onto Fe(II/III)-Kao surfaces through its polar head groups. The research results establish a theoretical foundation for further investigations on fine clay particle interface control and hydrophobic modifier design, ultimately guiding practical production processes.

Symmetric Electrochemical Supercapacitors Based on Electrodes of Graphene Nanoribbons/Iron-Doped Lanthanum-Strontium-Manganese Based Perovskite Oxides

The dramatic increase in the world population and industrialization have resulted in unprecedented levels of humanity's hunger for energy. The total global energy production has increased from 23 in 1900 to 548 Exajoules (1018 J = EJ) in 2016.1 A significant contribution of the internment renewable energy resources to the energy production before the mid of this century becomes a necessity to significantly reduce fossil fuel usage and hence limit global warming.1 This creates a great incentive to identify the best ways to store energy when it is not needed.Supercapacitors have gained significant attention due to their fast charging/discharging speed, high power density, and long-term cycling stability in contrast to traditional batteries.2 In recent years, perovskites and graphene nanoribbons have been significantly considered promising materials for electrochemical energy storage. The graphene-based materials have a highly tunable surface area, outstanding electrical conductivity, good chemical stability, and excellent mechanical behavior.3 While the perovskite materials provide the possibility of both anionic and cationic storage mechanisms.4 This presentation reports the in situ preparation of iron-dopped lanthanum-strontium-manganese-based perovskite oxides (La0.7Sr0.3MnxFe1-xO3-δ, LSMFO) in the presence of graphene nanoribbons (GNRs), and the evaluation of the supercapacitive behavior of the synthesized composites. The physical/chemical structure of LSMFO was evaluated using XRD, TEM, FT-IR, Raman spectroscopy, EDS, BET, and XPS. Integrating the perovskite materials that possess redox reaction ability with graphene nanoribbons that exhibit good electronic properties is found to improve the supercapacitor performance in comparison to the single components. The symmetric supercapacitor devices based on LSMFO/GNRs showed good stability (capacitive retention of 95% over 10,000 cycles at a higher current density of 10 A g-1), a wide potential window (up to 1.7 V), and a relatively high capacitance. The best composite with optimum LSMFO:GNRs ratio that shows the highest supercapacitance is identified and explained in correlation with its surface chemical structure. References G. A. Jones and K. J. Warner, Energy Policy, 93, 206–212 (2016).S. Ghosh, K. Anbalagan, U. N. Kumar, T. Thomas, and G. R. Rao, Applied Materials Today, 21, 100872 (2020).O. D. Salahdin et al., Appl. Phys. A, 128, 703 (2022).B.-M. Kim et al., Sci Rep, 12, 10043 (2022).

Hydrochromic xanthylium cations with tuneable colour and high moisture-sensitivity for potential smart packaging

Hydrochromic materials exhibit a colour change in response to water and moisture. Intensely coloured xanthylium cations, generated by acidifying xanthene-9-ol precursors with trifluoroacetic acid (TFA), are found to exhibit dramatic decolourization with high moisture-sensitivity. Mechanistic study confirms that the hydrochromic mechanism of xanthylium cations involves the nucleophilic addition of water molecules at the carbocation centre at 9-position of xanthylium, thus regenerating xanthene-9-ol. This accounts for the high reversibility with up to 50 acid-activation/moisture-deactivation cycles. Furthermore, functionalizing the cations with different aliphatic and aromatic groups (electron rich, electron poor and extended pi-conjugated moieties) at the 9- and 2,7-positions, enables the tuning of colour and moisture sensitivity of this hydrochromic system, by controlling the cations’ frontier molecular orbital energies and optical bandgap, as well as their chemical stability and nucleophilicity. To demonstrate the potential of the hydrochromic system for humidity sensing in smart packaging, optical paper probes and polymer films pre-doped with xanthene-9-ol precursors were prepared. Upon activation with TFA fume, they reveal different colour and decolourization rate in response to atmospheric moisture, ranging from minutes to hours, demonstrating feasibility for smart packaging and other potential applications.

Suppression of Cation Intermixing Highly Boosts the Performance of Core-Shell Lanthanide Upconversion Nanoparticles.

Lanthanide upconversion nanoparticles (UCNPs) have been extensively explored as biomarkers, energy transducers, and information carriers in wide-ranging applications in areas from healthcare and energy to information technology. In promoting the brightness and enriching the functionalities of UCNPs, core-shell structural engineering has been well-established as an important approach. Despite its importance, a strong limiting issue has been identified, namely, cation intermixing in the interfacial region of the synthesized core-shell nanoparticles. Currently, there still exists confusion regarding this destructive phenomenon and there is a lack of facile means to reach a delicate control of it. By means of a new set of experiments, we identify and provide in this work a comprehensive picture for the major physical mechanism of cation intermixing occurring in synthesis of core-shell UCNPs, i.e., partial or substantial core nanoparticle dissolution followed by epitaxial growth of the outer layer and ripening of the entire particle. Based on this picture, we provide an easy but effective approach to tackle this issue that enables us to produce UCNPs with highly boosted optical properties.

Assessing cationic dye adsorption mechanisms on MIL-53 (Al) nanostructured MOF materials using quantum chemical and molecular simulations: Toward environmentally sustainable wastewater treatment

The escalating levels of environmental pollutants, particularly cationic dyes, present a significant ecological threat. Cationic dyes such as rhodamine B (RB) and methylene blue (MB) are extensively used in diverse industrial applications and are known to exert detrimental effects on the environment. The focus of this study revolves around comprehensively examining the adsorption mechanisms associated with the binding of cationic dyes, namely, RB and MB, onto pristine and carboxylic acid (CXA)-modified MIL-53 (Al) nanostructures. By employing quantum mechanics and molecular simulations, this research elucidates the molecular-level behavior of materials and dyes during the adsorption process. The findings demonstrate that incorporating CXA groups enhances MIL-53 (Al)'s adsorption capacity for both RB and MB dyes. Furthermore, the simulations unveil that RB and MB dye adsorption onto the unmodified and modified MIL-53 (Al) materials occurs primarily through electrostatic, van der waals interactions, π-π stacking, and hydrogen bonding. Notably, RB dye exhibits superior reactivity and stability compared to MB dye, owing to its higher adsorption energy. This study provides valuable insights into cationic dye adsorption on nanostructured MIL-53 (Al), emphasizing the suitability of CXA-modified MIL-53 (Al) nanostructures for cationic dye removal from contaminated wastewater. The outcomes of this investigation hold the potential for developing cutting-edge technologies exhibiting superior efficiency and effectiveness for removing cationic dyes, thereby contributing to environmental preservation and public health. Ultimately, this study highlights the prospects of leveraging quantum mechanics and molecular simulations to anticipate the behavior of nanostructured materials and optimize their properties for wastewater treatment.

The Mechanical Properties Relationship of Radiation-Cured Nanocomposites Based on Acrylates and Cationic Polymerized Epoxies and the Composition of Silane-Modified Tungsten Disulfide Nanoparticles.

The effect of semiconducting tungsten disulfide (WS2) nanoparticles (NPs), functionalized by either methacryloxy, glycidyl, vinyl, or amino silanes, has been studied in photocuring of acrylate and epoxy resins (the latter photocured according to a cationic mechanism). The curing time, degree of curing (DC), thermal effects, and mechanical properties of the radiation-cured resins were investigated. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analyses confirmed that a silane coating was formed (1-4 nm) on the NPs' surface having a thickness of 1-4 nm. Fourier transition infrared (FTIR) was used to determine the DC of the nanocomposite resin. The curing time of the epoxy resin, at 345-385 nm wavelength, was 10 to 20 s, while for acrylate, the curing time was 7.5 min, reaching 92% DC in epoxy and 84% in acrylate. The glass transition temperature (Tg) of the photocured acrylates in the presence of WS2 NPs increased. In contrast to the acrylate, the epoxy displayed no significant variations of the Tg. It was found that the silane surface treatments enhanced the DC. Significant increases in impact resistance and enhancement in shear adhesion strength were observed when the NPs were treated with vinyl silane. A previous study has shown that the addition of WS2 NPs at a concentration of 0.5 wt.% is the optimal loading for improving the resin's mechanical properties. This study supports these earlier findings not only for the unmodified NPs but also for those functionalized with silane moieties. This study opens new vistas for the photocuring of resins and polymers in general when incorporating WS2 NPs.

High-performance new photoinitiators for the preparation of functional photocurable polymer composites

Obtaining dental composites with the desirable physical, mechanical and visual properties that polymerise according to an environmentally friendly cationic mechanism is a significant challenge. This is due to the lack of high-performance initiators for this type of material. This is because there are dental composites on the market that have, among other things, toxic monomers such as BisGMA. This paper presents five high-performance, completely new iodonium derivatives of biphenyl-based iodonium salts differentiated by push–pull structure of chromophores determined by positions of methoxy and trisilyl groups in the biphenyl rings. The influence of the methoxy grouping in the biphenyl ring on the push–pull effect was explained, and their spectroscopic and electrochemical properties were determined. For the first time, the possibility of using these compounds as high-performance initiators of cationic and radical polymerization was presented and described. New two-component initiator systems composed of iodonium salts and thiadiazole derivatives for preparing new-generation dental composites have also been proposed. The thiadiazole derivative was an very effective alternative to camphorquinone, commonly used in the dental industry. Completely new organic matrix compositions and a new curing mechanism have also been proposed by introducing monomers that polymerize according to radical and cationic mechanisms. As a result, dental composites with significantly reduced polymerization shrinkage compared to commercially available materials were obtained. Finally, a new photoinitiating system we have developed, makes it possible to obtain new composites that are an exciting alternative to materials currently used in dentistry.

Unraveling the Mechanism of Alkali Metal Fluoride Post-Treatment of SnO2 for Efficient Planar Perovskite Solar Cells.

The facile synthesis and beneficial properties of tin oxide have driven the development of efficient planar perovskite solar cells (PSCs). To increase the PSC performance, alkali salts are used to treat the SnO2 surface to minimize the defect states. However, the underlying mechanism of alkali cations' role in the PSCs needs further exploration. Herein the effect of alkali fluoride salts (KF, RbF, and CsF) on the properties of SnO2 and PSC performance is investigated. The results show different alkali have significant roles depending on their nature. Larger cations Cs+ preferably locate at the SnO2 film surface to passivate surface defects and enhance conductivity, while smaller cations like Rb+ or K+ cations tend to diffuse into the perovskite layer to reduce trap density of the material. The former effect leads to enhanced fill factor while the latter effect increases the open circuit voltage of the device. It is then demonstrated that a dual cation post-treatment of the SnO2 layer with RbF and CsF achieves PSC with a significantly higher power conversion efficiency (PCE) of 21.66% compared to pristine PSC with a PCE of 19.71%. This highlights the significance of defect engineering of SnO2 using selective multiple alkali treatment to improve PSC performance.

Interfacial binding rope theory of ion transport in sub-nanochannels and its application for osmotic energy conversion

Osmotic energy conversion is a promising method of sustainable electricity generation using seawater and river water. Artificial pure NaCl solutions are commonly used, whereas the effects of multivalent-ion ingredients present in natural seawater on osmotic power generation remain unclear. In this study, the impacts of coexisting ions in multicomponent seawater (MS) are experimentally assessed using graphene oxide membrane (GOM). Divalent cation in MS shows inferior transport to monovalent cation, thereby presenting a lower power density than when using pure NaCl solutions. Inspired by experimental results, an interfacial binding rope theory is proposed to clarify ion-wall interactions and cation transport in sub-nanochannels with hydrophilic functional groups. The binding rope networks include direct cation-wall connections mediated by composition-changed hydration shells, indirect connections by H-bonds linking solvated water molecules and functional groups, and electrostatic attractions between cations and negatively charged surfaces. The theory feasibility is confirmed by first-principles calculations focusing on the charge distribution, binding site and length, surface electrification, and cation diffusivity and selectivity in GOM sub-nanochannels. Divalent cation diffuses slower than monovalent cation in both pure solutions and confined channels. For the mixed solution in channels, both monovalent and divalent cations show worse diffusivities due to additional monovalent-divalent electrostatic repulsions, as well as inferior cation selectivity due to weakened deprotonation reactions. Bridged by environment-controlled interfacial potential distribution, ion diffusivity, and ion selectivity, this theory guides the improvement of MS-based osmotic performance under regulations of concentration gradient, pH, and temperature. A power density of 8.52 W m–2 and stable output within 27 days are achieved. The interfacial binding rope theory could be popularized to refine the transport mechanisms of various cations in diverse hydrophilic sub-nanochannel materials, promoting the application of osmotic power generation and other nanoscale technologies.

Experimental and theoretical insights into cationic polymerization of para-N,N-dimethylaminostyrene

The cationic polymerization electron-rich para-N,N-dimethylaminostyrene (DMAS) for high-molecular-weight polymer is few and highly challenging because of the ease reaction of N,N-dimethylamino group with proton or carbocation. In this contribution, three kinds of initiating systems including Lewis’s acid (BF3•OEt2), Brønsted acid (CF3SO3H, TfOH), and the carbocation system (IBVE-HCl/SnCl4, IBVE: isobutyl vinyl ether) were used in DMAS polymerization·BF3•OEt2 showed the highest efficiency for DMAS polymerization to afford high-molecular-weight poly(para-N,N-dimethylaminostyrene) (PDMAS). Copolymerizations of DMAS and 4-methoxystyrene (MOS) were unsuccessful no matter what the monomer feeding mode was, which only produced PDMAS or the blends of two homopolymers. Polymer chain-end analysis and NMR analysis of the intermediate showed that DMAS polymerizations obeyed cationic chain polymerization mechanism. Comprehensive theoretical DFT studies were performed to gain insight into the polymerization mechanism of DMAS. The chain transfer to the dimethylamino group of DMAS monomer was clearly found to be unique and curial to unexpected DMAS polymerization behavior.

Degradation of poly(1,3‐dioxolane). Depolymerization versus hydrolysis

AbstractThere is renewed interest in polymers of 1,3‐dioxolane (DXL), especially as components of degradable polymer networks. DXL, a five‐membered cyclic acetal, is easily available on a commercial scale. Due to the relatively low strain of the five‐membered ring, its polymerization proceeding by a cationic mechanism is reversible. Above the ceiling temperature in the presence of an acid catalyst, it therefore undergoes depolymerization and this is one of the possible ways of degradation. On the other hand, monomeric units within the poly(1,3‐dioxolane) (PDXL) chain are connected by acetal bonds that are susceptible to acid‐catalyzed hydrolysis and this offers an alternative route for PDXL chain degradation. Polymer networks with connecting PDXL blocks are designed as commodity plastic materials but also as gels intended for biomedical applications. In both applications the possibility of gel disintegration by controlled degradation of connecting PDXL blocks is advantageous. The degradation in the two instances should proceed under different conditions, however. Degradation of commodity plastic material may proceed at higher temperatures in ‘dry’ conditions while biomaterials should degrade at mild physiological temperatures in an aqueous environment. In published papers, the distinction between the two routes of degradation is not always considered. In the present mini‐review, both mechanisms of degradation are presented and the available information on PDXL bloc degradation is critically evaluated. © 2023 Society of Industrial Chemistry.

Insights into the influence mechanism of different interlayer cations on the hydration activity of montmorillonite surface: A DFT calculation

Montmorillonite is one of the main components of mudstones. Physical changes in the microstructure of montmorillonite after water absorption are the root cause of softening and disintegration of mudstone and the deterioration of bearing properties. In this study, the adsorption behavior and hydration mechanism of water molecules on the surface of four cationic forms of montmorillonites (LiMt, NaMt, KMt, and CaMt) were investigated by density functional theory (DFT). The results indicated that water molecules were adsorbed mainly through electrostatic attractive force with interlayer cations. The electrostatic attraction decreased in the following order: Ca-Mt > Li-Mt > Na-Mt > K-Mt; and CaMt demonstrated the strongest adsorption capacity. When adsorption occurred, there was a large charge transfer between the atom of a water molecule (Ow) and interlayer cations, and the hybridization of Ow 2p orbitals with Li 1 s, Na 3 s, K 4 s, and Ca 4 s orbitals formed bonds with certain ionic characteristic. This work directly explained the interaction mechanism of water molecules with montmorillonite at the atomic and electronic levels, which provided a new perspective to understand the adsorption process of water molecules on clay mineral surfaces.

Squalene hopene cyclases and oxido squalene cyclases: potential targets for regulating cyclisation reactions

Squalene hopene cyclases (SHC) convert squalene, the linear triterpene to fused ring product hopanoid by the cationic cyclization mechanism. The main function of hopanoids, a class of pentacyclic triterpenoids in bacteria involves the maintenance of membrane fluidity and stability. 2, 3-oxido squalene cyclases are functional analogues of SHC in eukaryotes and both these enzymes have fascinated researchers for the high stereo selectivity, complexity, and efficiency they possess. The peculiar property of the enzyme squalene hopene cyclase to accommodate substrates other than its natural substrate can be exploited for the use of these enzymes in an industrial perspective. Here, we present an extensive overview of the enzyme squalene hopene cyclase with emphasis on the cloning and overexpression strategies. An attempt has been made to explore recent research trends around squalene cyclase mediated cyclization reactions of flavour and pharmaceutical significance by using non-natural molecules as substrates.

Green Synthesis of Size-Controllable Polyfurfuryl Alcohol Nanospheres as Novel Bio-adsorbents

Nanomaterials derived from biomass preparation exhibit potential applications in the field of environmental protection. However, the synthesis methods still have some problems, including being a time-consuming and complex process and causing secondary pollution. In this work, polyfurfuryl alcohol (PFA) nanospheres are synthesized via a green method that uses water as the solvent, sodium dodecyl sulfate as the stabilizer, and p-benzenesulfonic acid monohydrate as the acid catalyst. In addition, the filtrate remained capable of preparing uniform nanospheres in five subsequent runs. Moreover, the size of PFA nanospheres could be regulated from 40 to 800 nm. The small PFA nanospheres provide a large surface area, suggesting more adsorption sites. PFA nanospheres are used first as novel bio-adsorbents for cationic dye (methylene blue) removal because of their abundant oxygen-containing functional groups and negative potential. Synthesis parameters and adsorption conditions affecting cationic dye removal, sorption mechanisms, and kinetics were studied. Results suggest that the synergistic effect of electrostatic attraction, π–π interactions, and hydrogen bonding contributes to the maximum adsorption capacity as high as 343.3 mg/g. Furthermore, the PFA nanospheres exhibited good regenerative properties. This work paves the way for the green and sustainable preparation of biomass furfuryl alcohol nanospheres.

Nature-inspired interfacial engineering for highly stable Zn metal anodes

Aqueous zinc-ion batteries (ZIBs) emerge as a potential candidate for large-scale energy storage applications, due to their low cost, eco-friendliness, and high safety. However, nowadays, ZIBs still suffer from poor cycling stability, owing largely to the severe dendrite growth, corrosion, and hydrogen evolution at the electrolyte/anode interface. Herein, inspired by the biomolecule-assisted cationic transport mechanism in nature, we apply humic acid (HA, a natural ingredient of soil) on the Zn surface for stabilizing the anode/electrolyte interface. Density functional theory calculations indicate that the tuned interactions between Zn2+ and the segments of HA possibly facilitate the desolvation of Zn2+. The theoretical results are supported by the electrochemical analyses, where the HA-induced interfacial layer promotes the reversible Zn deposition kinetics and suppresses the corrosion and hydrogen evolution. The improved electrochemical performance is validated by Zn/MnO2 coin and pouch cells. These findings not only provide insights into engineering electrolyte/electrode interfaces but also suggest that a broader family of materials, structures, and mechanisms in nature can be leveraged for more sustainable batteries.

1,4]Diazocine-Embedded Electron-Rich Nanographenes with Cooperatively Dynamic Skeletons.

Curved nanographenes (NGs) are emerging as promising candidates for organic optoelectronics, supramolecular materials, and biological applications. Here we report a distinctive type of curved NGs bearing a [1,4]diazocine core that is fused with four pentagonal rings. This is formed by Scholl-type cyclization of two adjacent carbazole moieties through an unusual diradical cation mechanism followed by C-H arylation. Owing to the strain in the unique 5-5-8-5-5-membered ring skeleton, the resulting NG adopts an interesting concave-convex cooperatively dynamic structure. By peripheral π-extension, a helicene moiety with fixed helical chirality can be further mounted to modulate the vibration of the concave-convex structure, through which the distant bay region of the curved NG inherits the chirality of the helicene moiety in a reversed fashion. The [1,4]diazocine-embedded NGs show typical electron-rich characteristics and form charge transfer complexes with tunable emissions with a series of electron acceptors. The relatively protruding armchair edge also allows the fusion of three NGs into a C2 symmetric triple diaza[7]helicene which reveals a subtle balance of fixed and dynamic chirality.

Nitrocellulose-based propellants: elucidation of the mechanisms of the diphenylamine stabilizer employing density functional theory

ABSTRACT The decomposition of energetic materials, especially propellants, produces nitrous gas and free acid nitrates which accelerates its rate velocity. To inhibit this inconvenient autocatalytic reaction, molecules known as stabilizers are usually included in their composition. One of them, diphenylamine (DPA), is primarily used in single-base compositions. In this work, we used density functional theory, with the RI-B2PLYP-D3BJ exchange-correlation functional, to investigate the N-nitrosation mechanism corresponding to a reaction between DPA and a nitro compound producing N-nitroso-diphenylamine (NNDPA). For this purpose, geometry optimizations (equilibrium and transition states), minimum energy paths, Gibbs free activation energies, and rate constants of four reaction mechanisms were computed both in the gas phase and simulating the nitrocellulose environment, which produced similar results. We found that the N-nitrosation mechanism with HNO2 is the most favored, with a rate constant of 5.3 × 10 −4 g·µmol −1 ·s −1. In contrast, the formation of NNDPA is less likely to depend on NO+ in agreement with the experimental results. Cationic reaction mechanisms are hardly viable, whereas interactions with NO or N2O3 are possible. Nonetheless, the former is too slow (1.02 × 10 −35 g·µmol −1 ·s −1) and the latter depends on the scarcely available nitro compound as a reactant, despite being considerably fast (1.61 × 104 g·µmol−1 ·s−1).

Cationic Single-Unit Monomer Insertion (cSUMI): From Discrete Oligomers to the α-/ω-End and In-Chain Sequence-Regulated Polymers

Single-unit monomer insertion (SUMI) has become an important strategy for the synthesis of sequence-controlled vinyl polymers due to its strong versatility and high efficiency. However, all reported SUMI processes are based on a free-radical mechanism, resulting in a limited number of monomer types being applicable to SUMI or a limited number of sequences of structural units that SUMI can synthesize. Herein, we developed a novel SUMI based on a cationic mechanism (cSUMI), which operates through a degenerative (similar to radical SUMI) but cationic chain transfer process. By optimizing the chain transfer agent (CTA) and monomer pairs, a high-efficiency cSUMI was achieved for vinyl ether and styrene monomers. Based on this reaction, a range of discrete oligomers containing vinyl ether and styrene moieties, and even α-/ω-end and in-chain sequence-regulated polymers were synthesized, most of which cannot be achieved by radical SUMI. In addition, we explored the application of these sequence-regulated polymers in the preparation of miktoarm star polymers, delivery of photosensitizers, and solubilization of fluorescence probes. The development of SUMI with a new mechanism will certainly broaden the scope of structures and sequences in precise vinyl-based polymers.

Investigating the Synthesis and Characteristics of UV-Cured Bio-Based Epoxy Vegetable Oil-Lignin Composites Mediated by Structure-Directing Agents.

Bio-based composites were developed from the epoxy derivatives of Lallemantia iberica oil and kraft lignin (ELALO and EpLnK), using UV radiation as a low energy consumption tool for the oxiranes reaction. To avoid the filler sedimentation or its inhomogeneous distribution in the oil matrix, different structure-directing agents (SDA) were employed: 1,3:2,4-dibenzylidene-D-sorbitol (DBS), 12-hydroxystearic acid (HSA) and sorbitan monostearate (Span 60). The SDA and EpLnK effect upon the ELALO-based formulations, their curing reaction and the performance of the resulting materials were investigated. Fourier-transform Infrared Spectrometry (FTIR) indicates different modes of molecular arrangement through H bonds for the initial ELALO-SDA or ELALO-SDA-EpLnK systems, also confirming the epoxy group's reaction through the cationic mechanism for the final composites. Gel fraction measurements validate the significant conversion of the epoxides for those materials containing SDAs or 1% EpLnK; an increased EpLnK amount (5%), with or without SDA addition, conduced to an inefficient polymerization process, with the UV radiation being partially absorbed by the filler. Thermo-gravimetric and dynamic-mechanical analyses (TGA and DMA) revealed good properties for the ELALO-based materials. By loading 1% EpLnK, the thermal stability was improved to with 10 °C (for Td3%) and the addition of each SDA differently influenced the Tg values but also gave differences in the glassy and rubbery states when the storage moduli were interrogated, depending on their chemical structures. Water affinity and morphological studies were also carried out.

Effects and mechanisms of anion and cation on the gelation of nanosilica sol by all-atom molecular dynamics simulation: promotion or inhibition?

Nanosilica sol (NSS) is prone to gelation due to the condensation of silicon hydroxyl at normal temperature and pressure, which is further exacerbated by the addition of electrolytes during production. Therefore, the effects of ions and the mechanism of gelation of NSS are crucial for its stability. Herein, all-atom molecular dynamics (AAMD) was carried out to explore the effects and mechanisms of cations (K+, Na+, Ca2+) and anions (Cl-, NO3-, SO42-, PO43-) on the sol-gel transition. Results indicated that highly electrophilic cations (e.g., Ca2+) and anions with slightly stronger nucleophilicity than Si(OH)3O- (e.g., NO3-) could inhibit gelation by preventing Si(OH)4 and Si(OH)3O- from approaching the silica surface. Such inhibition is more pronounced in NSS with larger particle sizes. Our findings offer some critical insights into the effects of ions on the gel stability of NSS, which also contributes significantly to screening suitable electrolytes for the production of NSS.