Low Transition Temperature Mixtures Research Articles

Freezing-Tolerant Supramolecular Adhesives from Tannic Acid-Based Low-Transition-Temperature Mixtures.

Natural polyphenols like tannic acid (TA) have recently emerged as multifunctional building blocks for designing advanced materials. Herein, we show the benefits of having TA in a dynamic liquid state using low-transition-temperature mixtures (LTTMs) for developing freezing-tolerant glues. TA was combined with betaine or choline chloride to create LTTMs, which direct the self-assembly of guanosine into supramolecular viscoelastic materials with high adhesion. Molecular dynamics simulations showed that the structural properties of the material are linked to strong hydrogen bonding in TA-betaine and TA-choline chloride mixtures. Notably, long-term and repeatable adhesion was achieved even at -196 °C due to the binding ability of TA's catechol and gallol units and the mixtures' glass transition temperature. Additionally, the adhesives demonstrated injectability and low toxicity against fibroblasts in vitro. These traits reveal the potential of these systems as bioadhesives for tissue repair, opening new avenues for creating multifunctional soft materials with bioactive properties.

A DES or LTTM: Eco-friendly solvent mediums for conversion of biomass to levulinic acid as a key chemical

In this study, the effect of using environmentally friendly, less toxic, low cost, and easily recyclable deep eutectic solvent (DES) and low-transition temperature mixture (LTTM), which are alternatives to ionic liquids, on the conversion of biomass to levulinic acid (LA) was investigated. The reaction conditions such as temperature, the amount of feedstock, and the water ratio were optimized to ensure maximum product formation in DES (ChCl-EG)-water medium. The highest amount of LA (143.2 ± 2.5 mg) under optimum reaction conditions was achieved by using glucose in a newlydesignedLTTM (SA:EG)-water solvent medium. Newly designed low-transition temperature mixture (SA:EG) characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and differential scanning calorimetry (DSC) analyses. A comprehensive theoreticalstudy was also performed to provide a deep understanding of the formation mechanisms of new LTTM by density functional theory (DFT), reduced density gradient (RDG), frontier molecular orbitals (FMOs), and molecular electrostatic potential (MEP) methods. The glucose conversion ratio increased from 70.2 % to 96.1 % in SA:EG-water medium. When microcrystalline cellulose, corn straw, and sorghum were used under the same conditions, 118.9 ± 5.4, 36.8 ± 9.4, and 32.6 ± 3.4 mg of LA were obtained per g of feedstock. A typical Brønsted acid; phosphotungstic acid (H3O40PW12) showed high catalytic activity, resulting in 229.0 ± 0.32 mg of LA per g of glucose in SA:EG-water medium. This shows that the use of SA:EG LTTM for cellulosic/lignocellulosic biomass sources can be used favorably in conversion reactions.

One-Pot Conversion of Starch into 5-Chloromethylfurfural and 5-Hydroxymethylfurfural in a Low-Transition Temperature Mixture

One-Pot Conversion of Starch into 5-Chloromethylfurfural and 5-Hydroxymethylfurfural in a Low-Transition Temperature Mixture

A Low Transition Temperature Mixture-based viscosupplementation complemented with celecoxib for osteoarthritis treatment

Viscosupplementation consists of hyaluronic acid (HA) intra-articular injections, commonly applied for osteoarthritis treatment while non-steroidal anti-inflammatory drugs (NSAIDs) are widely administered for pain relief. Here, HA and a NSAID (celecoxib) were combined in a formulation based on a low transition temperature mixture (LTTM) of glycerol:sorbitol, reported to increase celecoxib’s solubility, thus rendering a potential alternative viscosupplement envisioning enhanced therapeutic efficiency. The inclusion of glucosamine, a cartilage precursor, was also studied. The developed formulations were assessed in terms of rheological properties, crucial for viscosupplementation: the parameters of crossover frequency, storage (G’) and loss (G’’) moduli, zero-shear-rate viscosity, stable viscosity across temperatures, and shear thinning behaviour, support viscoelastic properties suitable for viscosupplementation. Additionally, the gels biocompatibility was confirmed in chondrogenic cells (ATDC5). Regarding drug release studies, high and low clearance scenarios demonstrated an increased celecoxib (CEX) release from the gel (6 to 73-fold), compared to dissolution in PBS. The low clearance setup presented the highest and most sustained CEX release, highlighting the importance of the gel structure in CEX delivery. NMR stability studies over time demonstrated the LTTM+HA+CEX (GHA+CEX) gel as viable candidate for further in vivo evaluation. In sum, the features of GHA+CEX support its potential use as alternative viscosupplement.

New low transition temperature mixture menthol:salicylaldoxime – a designer solvent for extraction of metal species

A new hydrophobic deep eutectic solvent was designed by combining menthol and salicylaldoxime.

Thermodynamic and molecular insights into the separation of ethanol/ethyl propionate by extraction using low transition temperature mixtures

Low-transition temperature mixtures (LTTMs) have been proposed as green solvents for the separation of ethanol (EtOH)/ethyl propionate (EtPa) azeotropes. COSMO-SAC model was used to screen LTTMs, and ammonium acetate, ethylammonium chloride, and choline chloride were selected as hydrogen bond acceptors to form LTTMs with ethylene glycol. Liquid-liquid phase equilibrium experiments were carried out for the screened LTTMs and the separation system to confirm the validity of the selected solvents. And the distribution coefficients of EtOH in the three LTTMs were all greater than 1.2, and the selectivity for EtOH ranged from 6 to 50. The separation mechanism at the molecular level was revealed through quantum chemical calculations and wave function analysis. The thermodynamic behavior of the EtOH/EtPa/LTTMs system and the role of hydrogen bonding interactions were systematically investigated. The results indicated that electrostatic forces are the main molecular interactions, and the stronger interaction of LTTMs with ethanol is the basis for achieving the azeotropic separation.

Nickel-Imidazolium Low Transition Temperature Mixtures with Lewis-Acidic Character.

Low transition temperature mixtures (LTTMs) are a new generation of solvents that have found extensive application in organic synthesis. The interactions between the components often generate highly activated, catalytically active species, thus opening the possibility of using LTTMs as catalysts, rather than solvents. In this work, we introduce a nickel-based imidazolium LTTM, study its thermal behavior and explore its catalytic activity in the solvent-free allylation of heterocycles with allylic alcohols. This system is effective in this reaction, affording the corresponding products in excellent yield without the need for additional purifications, thus resulting in a very environmentally friendly protocol.

Mechanistic Investigation of Isobutanol/Isobutyl Acetate Separation by Extraction Using Low-Transition Temperature Mixtures

Mechanistic Investigation of Isobutanol/Isobutyl Acetate Separation by Extraction Using Low-Transition Temperature Mixtures

Solid-phase extraction combined with dispersive liquid-liquid microextraction for the analysis of glucocorticoids in environmental waters using liquid chromatography-tandem mass spectrometry

This paper illustrates an enrichment procedure based on the combination of solid phase extraction (SPE) with dispersive liquid-liquid microextraction (DLLME) for the determination of ng/L concentration levels of glucocorticoids in river water samples. In SPE-DLLME, the target analytes were adsorbed by loading a large volume sample (200 mL) into an OASIS HLB cartridge (60 mg). After their desorption with a small volume of ethyl acetate (500 µL), this eluate was used as the dispersant in the following DLLME, performed on 5 mL of water, using a low transition temperature mixture (LTTM) as the extractant (100 µL). The LTTM was obtained by the heat-mixing of choline chloride and sesamol in a molar ratio 1:3 (ChCl:Ses, 1:3); when cooled, it was liquid at room temperature, denser than water and immiscible with it. The SPE-DLLME approach significantly limits the use of high volumes of organic solvents, avoids the evaporation step, and allows one to achieve an enrichment factor greater than 2500. All extracts were analysed by high-performance liquid chromatography-electrospray-tandem mass spectrometry. Eleven glucocorticoids, including the epimers dexamethasone/betamethasone, were separated on a polysaccharide-based column, based on cellulose tris(3‑chloro-4-methylphenylcarbamate) chiral selector. Recoveries ranged from 68 to 100% (spike level of 5 and 20 ng/L), with a LOD of 0.21-1.39 ng/L and a LOQ of 0.69-4.17 ng/L. The intra-day precision and inter-day precision were lower than 15%. After optimization and complete validation, the method was applied to analyze surface water samples, taken from River Tiber, to evaluate the effective applicability of the procedure and to establish the contamination levels for these substances.

CO2 absorption enhancement in low transition temperature mixtures-based nanofluids: Experiments and modeling

The enhancement of gas–liquid mass transfer in the CO2 absorption process by Low Transition Temperature Mixtures (LTTMs) based nanofluids was investigated. The effects of loading and size of TiO2 nanoparticles on the CO2 absorption rate were studied experimentally. The absorption rate was found to be improved significantly after adding nanoparticles. The maximum enhancement factor of 1.35 was observed when using nanoparticles with a particle size of 10 nm and a concentration of 0.6 kg/m3. The maximum absorption enhancement factor and mass transfer coefficient were observed when the loading of nanoparticles increased, hence there was an optimal concentration of TiO2 nanoparticles in the CO2 absorption process. For the size of nanoparticles, the CO2 absorption rate was higher when the diameter of nanoparticles decreased. Furthermore, a three-dimensional unsteady mathematical model of gas–liquid mass transfer, which was based on the mechanisms of grazing effect and hydrodynamic effect in the gas–liquid boundary layer, was developed to describe the CO2 absorption enhancement. The model predictions were well consistent with the experimental results, with a maximum deviation of less than 5%, which proved the reliability of the model. Finally, Molecular dynamics simulations were conducted on the absorbent-CO2 system. The results showed that the addition of TiO2 nanoparticles led to a reduction in the simulation box size at the same simulation time, but it did not significantly alter the interaction between LTTMs and CO2. Therefore, it can be inferred that TiO2 nanoparticles enhance CO2 absorption capacity by modifying the mass transfer rate. Through the aforementioned study, this paper explores the experimental and mechanistic aspects of nanoparticle-enhanced absorption of CO2 in LTTMs systems. The research demonstrates the feasibility of nanoparticle-enhanced absorption of CO2 in LTTMs solvents, providing insights into studying nanoparticle-enhanced gas–liquid mass transfer and offering a new research approach for CO2 capture.

Experimental and molecular dynamics simulation study of toluene absorption by nanofluids

It is well known that the emission of volatile organic compounds (VOCs) is a significant threat to human health and the ecological environment, and toluene is a typical representative of aromatic VOCs, whose elimination makes an important contribution to the prevention and control of air pollution. Absorption is the classical process to eliminate air pollutants, but the application of absorption is often constrained by absorbent and gas-liquid mass transfer. In recent years, process intensification has become an important development in the chemical industry, and nanotechnology can effectively reduce mass transfer resistance and improve gas-liquid mass transfer effectiveness. This work aims to evaluate the effect of adding nanoparticles on the gas-liquid mass transfer process. The effects of TiO2, Al2O3, and SiO2 nanoparticles on the removal of toluene by green solvent low transition temperature mixtures (LTTM) were investigated experimentally and theoretically. The mass transfer enhancement factors of the toluene absorption process were measured at different concentrations and sizes of TiO2, Al2O3, and SiO2 nanoparticles, absorption temperatures and number of cycles. Molecular dynamics (MD) simulations of the microscopic properties of LTTM and toluene were performed. Based on the MD simulation results, the toluene density distribution, interaction energy, radial distribution function, spatial distribution function, and self-diffusion coefficient were calculated, which helped to explain the absorption mechanism of toluene gas. The findings demonstrated that nanoparticles can alter the gas-liquid mass transfer process, and provided a method and theoretical reference for enhancing the toluene absorption process.

Preparation and Application of Polymeric Molecularly Imprinted Adsorbents in Accordance with the Principles of Green Chemistry

Molecularly imprinting technology is a suitable tool for the development of selective materials for the isolation and separation of substances, and targeted use. The aim of this paper was to compile an overview of current trends in the preparation of MIP (Molecularly Imprinted Polymers). We focused on the implementation of ecologically acceptable solutions in the procedures for the fabrication and application of MIP, mainly for the purposes of chemical analyses. Theoretical approaches and simulations for the selection of optimal components of the polymerization mixture, the application of ultrasonic and microwave light in MIP synthesis, as well as microextraction procedures for the preparation of complex samples for analysis are successfully applied in analytical methods based on MIP adsorbents. While the use of low transition temperature mixtures (deep eutectic solvents, ionic liquids) and biomass components as a replacement or modification of porogens, functional and cross-linking monomers or other components of the polymerization mixture can help to transform the polymerization processes into more environment-friendly ones, it still requires an investigation of the synthesis mechanisms and their influence on the properties of the prepared MIPs.

Optimization Study of Glucose Synthesis to 5-Hydroxymethylfurfural (5-HMF) by Using Low Transition-Temperature Mixtures (LTTM)

5-Hydroxymethylfurfural (5-HMF) is a potential value-added product gaining popularity due to its wide range of applications. Glucose is widely used for 5-HMF production because it is abundant and more cost-effective than other resources. In the current research, a combination of microwave irradiation and low transition-temperature mixture (LTTM) for 5-HMF production was sustainably created. A preliminary study was conducted to derive 5-HMF using LTTM as a green solvent in various ratios of glucose: LTTM (MA/ChCl): water (10:100:15) and (10:48:100) via microwave heating at 90 °C for 10–60 min reaction time. The product analysis revealed that the 10:100:15 combination ratio of glucose: LTTM: water produced more 5-HMF (20.5%) than the 10:48:100 (0.28%) ratio. Following the preliminary results, an optimization study was conducted, focusing on the reaction temperature, LTTM mass, and water to assess the impact on 5-HMF yield and glucose conversion, using CCD in Design-Expert software. The quadratic model fit for 5-HMF yield and the 2FI model for glucose conversion yielded R2 values of 0.9861 and 0.8610, respectively. Both responses had a significant p value of 0.0061 for glucose conversion and <0.0001 for 5-HMF yield. An optimum point was achieved at 100 °C, 100 g of LTTM, and 20 g of water, with an expected 5-HMF yield and glucose conversion of 45.77% and 69.03%, respectively.

RHEOLOGICAL STUDY ON THE PARAMETERS AFFECTING THE VISCOSITY OF THE GREEN SOLUTION CONSISTING SLS AND LTTM

Enhanced Oil Recovery (EOR) is known to effectively improve oil recovery by producing the residual oil saturation in a reservoir. Many chemicals for injected fluid in EOR are synthetic and harmful to the environment. Aims: This study aims to characterize a newly developed green solution consisting of Sodium Lignosulfonate (SLS) and a Low Transition Temperature Mixture (LTTM) for injection agent. Methodology and Results: The concentration of surfactant was defined using weight percentage, which was calculated from the portion of the total weight of LTTM. The characterization was approached by analyzing the behavior of the green solution based on the power law analysis of the rheological measurement. The analyses of value, viscosity, shear rate, and shear stress were carried out. Increasing in viscosity was caused by the additional molecular mass of sucrose in the solution. This study found that the SLS concentration and LTTM ratio affects the rheological behavior of the green solution. Conclusion, significance, and impact study: According to the results, adding the SLS concentration increases the probability of the green solution becoming an EOR agent by showing shear-thinning behavior. Further studies are required to ensure the feasibility of the green solution during the injection period and the propagation in the reservoir.

κ-Carrageenan Associated with Fructose/Glycerol/Water LTTM: Toward Natural Thermosensitive Physical Gels

κ-Carrageenan was combined to a natural low-transition temperature mixture composed of fructose, glycerol, and water in a 1:1:5 molar ratio (FGW) to generate fully biobased physical gels through a simple method. The resulting gels can be easily prepared in various shapes. As for their hydrogel analogues, the rheological characterization of FGW-based samples evidenced thermosensitive gelation, attributed to the formation of aggregated H-bonded helices composed of κ-carrageenan chains. FGW-based gels exhibit a gel–sol transition temperature (Tg/s) higher than the one of hydrogels with recoverable and reversible viscoelastic properties upon successive heating/cooling cycles. SAXS analysis revealed a more extended conformation of chains in FGW that leads to more physical cross-linking junction zones within the materials. Such peculiar spatial internal organization provides a mechanical reinforcement demonstrated by compression tests. In conclusion, the use of the FGW solvent allows for designing κ-carrageenan physical gels with enhanced thermal and mechanical properties.

Separation of ethyl acetate-isopropanol using low transition temperature mixtures: Vapor-liquid equilibrium experiments and quantum chemical calculation

Ethyl acetate and isopropanol, as essential chemical ingredients and organic solvents, play an important role in the industry. At atmospheric pressure, ethyl acetate and isopropanol form an azeotrope, which can be separated by extractive distillation. The choice of extractant is critical in extractive distillation. Low transition temperature mixtures (LTTMs), which are emerging as efficient green solvents, are used as extractants in this work. The effect of type and structure on separation performance were studied, and three LTTMs were selected for the separation of the ethyl acetate-isopropanol system. The vapor–liquid equilibrium (VLE) data of ethyl acetate-isopropanol-LTTMs was measured by experiments, and the results showed that when the mole fraction of LTTMs was 0.1, all three LTTMs could break the azeotrope of ethyl acetate and isopropanol, especially LTTM1 (tetrabutylammonium bromide: ethanolamine = 1:2) having the best selectivity. To acquire the binary interaction parameters, the NRTL model was used to fit the experimental data, and the regression data was in good agreement with the experimental data. In addition, a quantum chemical method was used to investigate the interactions between molecules to gain insights into the microscopic mechanism. Results showed that the weak hydrogen bonding and van der Waals forces are formed between ethyl acetate and other systems, while moderate or weak hydrogen bonding are formed between isopropanol and other systems.

Oil palm residue as precursors for low transition temperature mixture extracted lignin

Lignin is a complex biopolymer in lignocellulosic biomass. It is a promising feedstock for producing various products, including chemicals and biofuels. Lignin extraction can be achieved via different routes such as organosolv, acid, alkaline, ionic liquids (ILs), and low transition temperature mixtures (LTTMs). LTTM is attractive for its biocompatibility, biodegradability, more straightforward synthesis procedure, lower precursor price, and toxicity than the aforementioned options. In this work, we report the use of an LTTM made from a combination of sucrose-malic acid-water (SMAW) to harvest lignin from four oil palm residues (i.e. empty fruit bunch (EFB), trunk (OPT), mesocarp fibre (MSF), and kernel shell (PKS)). There is still a knowledge gap on the applicability of SMAW to extract lignin from different oil palm residues. Limited studies have examined the properties of the SMAW-extracted lignin, particularly the lignin purity and thermal behaviour. Our results indicated SMAW as a sustainable LTTM solvent for lignin extraction for these four oil palm residues. EFB harvested the highest SMAW LTTM-extracted lignin yield of 27.23% with a lignin purity of 74.93%. TGA curves and DTG curves implied that the extracted lignin was thermally more reactive than alkaline lignin and served as an attractive precursor for thermochemical conversion processes.

Iron‐Based Imidazolium Salt as Dual Lewis Acid and Redox Catalyst for the Aerobic Synthesis of Quinazolines

AbstractA low transition temperature mixture formed with 1‐butyl‐3‐(methoxycarbonylmethyl)imidazolium chloride and iron(III) chloride has proven to be an efficient catalyst for the synthesis of quinazolines following a sequence of condensation‐cyclization‐oxidation reactions. The protocol is simple and effective for coupling 2‐acylanilines and benzylamines to form nitrogen containing heterocycles with moderate to excellent yields (up to 93 %), being possible to perform the reaction in preparative scale. The functionalized imidazolium salt is crucial for the activation of the reagents under solvent‐free conditions, and the presence of iron in the catalyst mediates the oxidation step with atmospheric oxygen. These features make the presented procedure better, from an environmental point of view, than other processes previously described. For this comparison, different “green” metrics have been used, such as atom economy, stoichiometric factor, reaction mass efficiency, E‐factor, and EcoScale.

Green and highly efficient synthesis of pyrimidine derivatives in a novel glycolic acid: urea‐based low transition temperature mixture via C–C and C–O bond formation

AbstractThe present works describe a highly efficient synthesis of pyrimidine derivatives through a Knoevenagel condensation followed by Michael addition and subsequent cyclization using novel designer Low Transition Temperature Mixture (LTTM) in Glycolic acid: Urea (1:1). The mixture afforded as a green solvent which plays a dual role as a reusable catalyst and solvent, simple to prepare and nontoxic. The thermal stability and working temperature range of low‐temperature mixture were identified by Thermogravimetric analysis and Differential Scanning Calorimetry. The pyrimidine derivatives synthesized via a one‐pot three‐component reaction of two moles of Barbituric/Thiobarbituric acid and one mole of aryl aldehydes reacted through Knoevenagel condensation followed by Michael addition and subsequent cyclization. The Knoevenagel intermediate formed at room temperate while at 80°C Knoevenagel intermediate further reacted with another mole of barbituric acid/Thiobarbituric acid and formed the cyclic compounds. The use of LTTM to yield vital pyrimidine molecules renders this protocol to cope with the current need for an efficient, cost‐effective, and eco‐friendly methodology.

Performance evaluation and molecular dynamics simulation in the Liquid–liquid extraction process of low transition temperature mixture + n-hexane + 1,2-Dichloroethane

Vinyl sulphate, a new battery additive, can significantly improve battery performance, but its production process generates a large amount of n-hexane + 1,2-dichloroethane (DCE) azeotropic mixtures. In this paper, green and efficient Low Transition Temperature Mixtures (LTTMs) were used as solvents to explore their separation performance and mechanism of the n-hexane + DCE azeotrope system. Firstly, the conductor-like screening model for segment activity coefficient (COSMO-SAC) model was used to investigate the effects of the structure and composition of the hydrogen bond donors and hydrogen bond acceptors on the extraction performance. On this basis, three LTTMs were screened out as solvents for the extraction and separation of n-hexane + DCE by combining experiments, which were trimethylamine hydrochloride-levulinic acid 1:2 (LTTM1), tetraethylammonium chloride-levulinic acid 1:2 (LTTM2), tetraethylammonium chloride-pyruvic acid 1:2 (LTTM3). Afterward, Liquid–liquid equilibrium (LLE) experiments were carried out for the ternary system of n-hexane + DCE + LTTMs, and the results showed that the extraction of DCE was favored by low temperatures in the experimental temperature range. Then, molecular dynamics simulation was used to investigate the microscopic mechanism of the extraction and separation of n-hexane + DCE by LTTMs. The results showed that the interaction between LTTMs and DCE was much larger than that between LTTMs and n-hexane, n-hexane and DCE, which was the fundamental reason for the separation of n-hexane + DCE by LTTMs. Finally, the continuous separation process of n-hexane + DCE was simulated using Aspen Plus, and the results showed that LTTMs had good extraction performance and the purity of n-hexane and DCE products could reach 99.6 mol% and 99.5 mol%, respectively. The feasibility and microscopic mechanism of the extraction and separation of n-hexane + DCE by LTTMs were investigated using a combination of experiments and simulations, which provided a methodological reference for the separation of n-hexane + DCE.