Ester Exchange Research Articles

Homogeneous and heterogeneous ionic liquids catalyze CO2 cycloaddition reaction

The synthesis of cyclic carbonates, which are essential solvents for lithium-ion batteries, through the cycloaddition of carbon dioxide (CO2) and epoxides, and further ester exchange with methanol to form linear carbonates has always been one of the effective ways for CO2 resource utilization. In this work, the kinetics and reactor technology selection of ionic liquids as catalysts for CO2 conversion were analyzed from the perspective of process systems engineering. Firstly, ethanol (EtOH) was used as the solvent, and 1‑butyl‑3-methylimidazolium bromide ([Bmim] Br) was used to catalyze the CO2 cycloaddition reaction in a batch reactor. The effect of reaction conditions on the kinetic performance of synthesizing propylene carbonate (PC) was studied. Secondly, a supported polyelectrolyte liquid membrane was designed and prepared, and a continuous ionic liquid membrane reactor was established for the continuous catalytic reaction of CO2 and epichlorohydrin (PO). The performance of the continuous catalytic reaction was studied and compared with batch reaction experiments. Based on the results of kinetic experiments, the reaction order of the reaction rate equation and the activation energy in the reaction system were determined. Finally, under the premise of achieving high PC yield goals and optimizing process conditions, a dual zone dynamic modeling was conducted on the batch reactor to guide the comprehensive evaluation of technology, economy, and environment under uncertain conditions, laying the foundation for the pilot scale clean production of high-value chemicals synthesized by chemical conversion of CO2.

High strength “breathable” glycosilicone/Aloe vera polysaccharide-based gel dressing for efficient wound repair

Medical wound dressings are effective in protecting wounds, maintaining moisture, creating an optimal healing environment and accelerating wound healing. However, their deficiencies in mechanical properties, adhesion and prevention of adhesion to the wound bed have been identified as limiting factors for their therapeutic efficacy in wound healing. To address these issues, we prepared glycosilicone gel dressings consisting of hydrophobic polysiloxanes and highly hydrophilic polysaccharides via ester exchange and silicone hydrogen addition reactions. Silicone gel dressings exhibit skin-like “respiratory” properties, with good permeability to O2 and CO2. Additionally, elongation and other important parameters are similar to those of the skin, which provides a foundation for the application of silicone gels in the field of wound dressings. The introduction of Aloe vera polysaccharide (AP) results in the glycosilicone gel exhibiting certain mechanical properties, including a tensile strength of 0.35 MPa and an adhesion force of 10 N/m. Furthermore, a mouse model of total skin defect demonstrated that the wound healing rate of the mice on the 12th day was 98 %, which effectively promotes wound healing. Consequently, the glycosilicone gel is anticipated to be an optimal wound dressing.

Study on a New Reactive Dividing-Wall Column for the Reaction of Vinyl Carbonate and Methanol Ester Exchange to Produce Dimethyl Carbonate

Study on a New Reactive Dividing-Wall Column for the Reaction of Vinyl Carbonate and Methanol Ester Exchange to Produce Dimethyl Carbonate

Spatial heterogeneity, sediment-water exchange, and diffusion mechanisms of organophosphate esters from river to coastal aquatic system in a typical economic circle of northern China

Organophosphate esters (OPEs) have proven to be pervasive in aquatic environments globally. However, understanding their partitioning behavior and mechanisms at the sediment-water interface remains limited. This study elucidated the spatial heterogeneity, interfacial exchange, and diffusion mechanisms of 14 OPEs (∑14OPEs) from river to coastal aquatic system. The transport tendencies of OPEs at the sediment-water interface were quantitatively assessed using fugacity methods. The total ∑14OPEs concentrations in water and sediments ranged from 154 ng/L to 528 ng/L and 2.41 ng/g dry weight (dw) to 230 ng/g dw, respectively. This result indicated a descending spatial tendency with moderate variability. OPE distribution was primarily influenced by temperature, pH, and dissolved oxygen levels. As the carbon atom number increased, alkyl and chlorinated OPEs transitioned from diffusion towards the aqueous phase to equilibrium. In contrast, aryl OPEs and triphenylphosphine oxide, which had equivalent carbon atom counts, maintained equilibrium throughout. Diffusion trends of individual OPE congener at the sediment-water interface varied at the same total organic carbon contents (foc). As the foc increased, the fugacity fraction values for all OPE homologs showed a declining trend. The distinct molecular structure of each OPE monomer might lead to unique diffusive behaviors at the sediment-water interface. Higher soot carbon content had a more pronounced effect on the distribution patterns of OPEs. The sediment-water distribution of OPEs was primarily influenced by total organic carbon, sediment particle size, dry density, and moisture content. OPEs displayed the highest sensitivity to fluctuations in ammonium and dissolved organic carbon. This study holds significant scientific and theoretical implications for elucidating the interfacial transport and driving forces of OPEs and comprehending their fate and endogenous release in aquatic ecosystems.

Self-healing, adaptive and shape memory polymer-based thermal interface phase change materials via boron ester cross-linking

Addressing the thermal resistance between rough interfaces without applying pressure to the interfacial sandwich has been a challenge. Herein, a thermal interface phase change material (TIPCM) is designed to realize a 3D support skeleton with a dynamic crosslinking network by introducing a boron ester crosslinking backbone into paraffin wax (PW) and ethylene-octene copolymer (EOC), thus enabling the TIPCM to ensure mechanical integrity without leakage even above the melting temperature of EOC. The chemical cross-linking between the organic solid–liquid phase change material (PCM) and the polymer realizes thermally triggered self-healing and adaptive shape memory properties. The phase transition of PW leads to a decrease in the modulus of TIPCM and activates the ester exchange of the dynamic covalent bonding of boron esters, which allows TIPCM to self-heal and self-adapt to a variety of object surfaces. These enabled the TIPCM to fill the interface gaps through small stress deformations, forming an interlocking structure that reduces contact thermal resistance and promotes heat transfer. The obtained TIPCM achieves excellent chip thermal management performance, cooling the analog CPU temperature by 67 °C at 5 V. In conclusion, this study provides a potential strategy for redesigning TIPCMs with high latent heat and special physical properties for thermal management.

Site-Selective Deuteration of α-Amino Esters with 2-Hydroxynicotinaldehyde as a Catalyst.

An efficient method has been developed for the synthesis of α-deuterated α-amino esters via hydrogen isotope exchange of α-amino esters in D2O with 2-hydroxynicotinaldehyde as a catalyst under mild conditions. This methodology exhibits a wide range of substrate scopes, remarkable functional group tolerance, and affording the desired products in good yields with excellent deuterium incorporation. Notably, the ortho-hydroxyl group and the pyridine ring of the catalyst play a crucial role in the catalytic activity, which not only stabilizes the carbon-anion intermediates but also enhances the acidity of the amino esters' α-C-H bond.

Exploring the dual dynamic synergy of transesterification and siloxane exchange in vitrimers

Despite the benefits of dynamic polymer networks with multiple dynamic bonds, identifying compatible combinations of dynamic chemistries that work synergistically to achieve desirable properties, remains a significant challenge. This work focuses on the potential of utilizing both siloxane and ester dynamic bonds in epoxy-acid cured vitrimers to finetune chemical exchange reactions. We identified to what extent a common basic catalyst (TBD) can simultaneously activate siloxane and ester exchange in the corresponding epoxy-based vitrimers. Our results showed that TBD is not only able to facilitate network formation but also improved the dynamic behavior of the resulting networks dramatically, with an overall exchange rate faster than the sum of the individual exchange chemistries, as shown by stress-relaxation studies. It has been demonstrated that the siloxane and ester dynamic bonds work together in a synergistic way to facilitate topology rearrangement. The relative increase or decrease in mobility of neighboring chains, located around a specific dynamic bond within the polymer network, was investigated in detail by adjusting the concentration of dynamic bonds and catalyst. The herein reported strategy allows the production of dual dynamic polymer networks that exhibit much shorter relaxation times and thus improved (re)processability in comparison to vitrimers with one type of dynamic bond.

Catalyst-Free and Sustainable Bio-Based Epoxy Vitrimer Prepared Based on Ester Exchange and Imine Bonding

Catalyst-Free and Sustainable Bio-Based Epoxy Vitrimer Prepared Based on Ester Exchange and Imine Bonding

Rhodium‐Catalyzed Regioselective C—O and C—C Bonds Formation of 3‐Oxopent‐4‐enenitriles with Alkynes for the Synthesis of Polysubstituted 2H‐Pyrans

Comprehensive SummaryThe rhodium‐catalyzed C—H bond activation and cyclization of 3‐oxopent‐4‐enenitriles with alkynes proceed efficiently. Various 2H‐pyrans with multiple substituents are achieved in good yields through regioselective formation of C—O and C—C bonds. Transformations involving hydroxy‐alkynoates resulted in products with a furo[3,4‐b]pyran skeleton via further intramolecular ester exchange processes. Different from the traditional “1‐oxatrienes pathway”, this method for the synthesis of useful 2H‐pyrans possesses certain highlights in terms of readily available substrates, stable and easily derivatized products, gentle and convenient operation process, and step and atom economy.

Examination of the effects of triacylglycerol lipase on astaxanthin conversion in the black tiger prawn Penaeus monodon

The enzyme triacylglycerol lipase (TGL) catalyses the hydrolysis of triacylglycerols, and is characterized by catalytic esterification and ester exchange functionality. However, at present, there is comparatively little information regarding the sequences and functional validation of TGLs in crustaceans. In this study, we cloned the TGL1 gene of the black tiger prawn Penaeus monodon. The full-length cDNA of PmTGL1 comprises 1807 base pairs (bp), including an 80-bp 5′-untranslated region (UTR), a 149-bp 3′-UTR, and a 1578-bp open-reading frame (ORF), and encodes a putative 525-amino acid protein of 58.71 kDa with a theoretical isoelectric point of 4.81. Homology and phylogenetic tree analyses revealed that PmTGL1 is most closely related to the TGL of Penaeus chinensis, with which it clusters in a single group (similarity of up to 97.52%). Quantitative real-time PCR analysis further revealed that PmTGL1 is most highly expressed in the shrimp hepatopancreas. Although the expression of PmTGL1 was not significantly influenced by the differences in the background colour of the rearing pond, it was significantly promoted in response to dietary supplementation with astaxanthin. As an adipokinetic hormone in P. monodon, PmRPCH (red pigment-concentrating hormone) plays an important role in body colour changes and lipid metabolism. Based on our findings, we speculate that the PmTGL1 facilitates astaxanthin metabolism in P. monodon via the hydrolysis of esterified astaxanthin to yield free astaxanthin and that the activity of TGL in these shrimps is regulated via an adipokinetic hormone cascade.

Total Outflow of High-Density Lipoprotein–Cholesteryl Esters from Plasma Is Decreased in a Model of 3/4 Renal Mass Reduction

(1) Background: Previous studies have enriched high-density lipoproteins (HDL) using cholesteryl esters in rabbits with a three-quarter reduction in functional renal mass, suggesting that the kidneys participate in the cholesterol homeostasis of these lipoproteins. However, the possible role of the kidneys in lipoprotein metabolism is still controversial. To understand the role of the kidneys in regulating the HDL lipid content, we determined the turnover of HDL-cholesteryl esters in rabbits with a three-quarter renal mass reduction. (2) Methods: HDL subclass characterization was conducted, and the kinetics of plasma HDL-cholesteryl esters, labeled with tritium, were studied in rabbits with a 75% reduction in functional renal mass (Ntx). (3) Results: The reduced renal mass triggered the enrichment of cholesterol, specifically cholesteryl esters, in HDL subclasses. The exchange of cholesteryl esters between HDL and apo B-containing lipoproteins (VLDL/LDL) was not significantly modified in Ntx rabbits. Moreover, the cholesteryl esters of HDL and VLDL/LDL fluxes from the plasmatic compartment tended to decrease, but they only reached statistical significance when both fluxes were added to the Nxt group. Accordingly, the fractional catabolic rate (FCR) of the HDL-cholesteryl esters was lower in Ntx rabbits, concomitantly with its accumulation in HDL subclasses, probably because of the reduced mass of renal cells requiring this lipid from lipoproteins.

Recyclable and shape‐memory hydantoin epoxy resins based on dynamic ester‐exchanged bonds

AbstractThe permanent crosslinked network imparts chemical and mechanical stability to crosslinked elastomers, making their recycling a serious environmental issue. The decomposition products of pentaaryl diazoxide in the structure of hydantoin epoxy resin are nitrogen and carbon dioxide, and it is an environmentally friendly resin material. Here, we demonstrate a reversible covalent bonding reaction catalyzed by Zn2+ between the ester bond formed by the hydantoin epoxy resin and the acid anhydride, and construct a reversible crosslinked network structure of the environmentally friendly acid anhydride/hydantoin epoxy resin material. The strength, hardness and toughness of the cured material are greatly improved by optimizing its ratio. The ester exchange bonding can be reversible with temperature, which leads to the shape memory capability of the synthesized cured material. The cured product of HMY1 was recovered with ethylene glycol and completely dissolved at 180°C for 11 h. Ethylene glycol was volatilized at 190°C to obtain decomposed epoxy oligomer (DEO), which was added to the HMY1 resin system (the amount of DEO was 30 wt% of the total mass of the resin), and the network structure was cross‐linked to enable it to be recovered and remanufactured. Thus, this work provides a new avenue for the environmentally friendly development of recyclable, reconfigurable, and thermally adaptable shape‐memory hydantoin epoxy materials.Highlights Hydantoin epoxy resin eventually breaks down into non‐toxic CO2 and N2. Hydantoin epoxy and methyl tetrahydrophthalic anhydride form a reversible dynamic chemical bond catalyzed by Zn2+. Ethylene glycol can recover and reuse the solidified product.

Investigation of the Impact of Castor Biofuel on the Performance and Emissions of Diesel Engines

Fossil fuel is a non-renewable fuel, and with the development of modern industry and agriculture, the storage capacity of fossil fuels is constantly decreasing. In this study, a systematic study and analysis were conducted on the combustion characteristics, engine performance, and exhaust emission characteristics of castor biodiesel–diesel blends and pure diesel fuel in different proportions at different speeds of a single-cylinder four-stroke diesel engine under constant load. The castor biodiesel required for the experiment is generated through an ester exchange reaction and mixed with diesel in proportion to produce biodiesel–diesel blends. The experimental results show that as an oxygenated fuel with a higher cetane number, the CO, HC, and smoke emissions of diesel and B80 blend fuel at 1800 rpm were reduced by 16.9%, 31.6%, and 68%, respectively. On the contrary, the NOx and CO2 emissions increased by 17.3% and 34.6% compared to diesel at 1800 rpm. In addition, due to its high viscosity and low calorific value, the brake thermal efficiency and brake-specific fuel consumption of the biodiesel–diesel blends are slightly lower than those of diesel, but the biodiesel–diesel blends exhibit lower exhaust gas temperatures. Comparing B80 and diesel fuel at 1800 rpm, the BSFC of diesel at 1800 rpm is 3.12 kg/W·h, whereas for B80 blended fuel, it increases to 4.2 kg/W·h, and BTE decreases from 25.39% to 21.33%. On the contrary, B60 blended fuel exhibits a lower exhaust emission temperature, displaying 452 °C at 1800 rpm. Based on the experimental results, it can be concluded that castor biodiesel is a very promising clean alternative fuel with low waste emissions and good engine performance.

Molecularly engineered cardanol derived epoxy vitrimers based on dynamic disulfide and dynamic ester exchanges with desirable dynamic response, degradability, and recyclability

Dynamic covalent chemistry provides a solution to the recycling problem of epoxy resins, and the graphene functional composites. Nevertheless, the study on chemical structures of the curing agent, and the type of dynamic covalent bonds associated with the nature of the epoxy resins still face challenge due to unclear mechanism and improper design strategy. Herein, a bio-based epoxy monomer was designed from cardanol, and used to fabricate a double dynamically crosslinked epoxy vitrimer. The mechanical properties, dynamic mechanical properties, thermal stability, relaxation behavior, self-healing efficiency, recovery, and reprocessing efficiency of the resulting resins were investigated, focusing on the effects of the soft and hard structure of the curing agent, and the types of dynamic covalent bonds. Bio-based epoxy vitrimers demonstrated several advantages, including multi-stimulus responsiveness, multi-channel self-healing ability, mechanical and chemical recovery, and biodegradability. Specifically, the epoxy vitrimers containing rigid furan rings exhibited better mechanical properties (6.85 MPa) and stability (Tg = 40.81 °C) compared to those with flexible fatty chains. Additionally, the double dynamically crosslinked vitrimer showed faster stress relaxation time (5.6 min) and lower activation energy (36.58 kJ/mol) compared to systems with a single dynamic bond. Finally, the addition of graphene enabled the production of cardanol-based composites with conductivity. Overall, the ease with bio-based epoxy vitrimer and its composites with excellent degradability can be fabricated, utilized, recycled and re-used, which is a novel direction for sustainable composites.

Fast Degradable and Thermally Conductive Silicone Rubber Vitrimer with Low Dielectric and UV‐Shielding Properties

AbstractSilicone rubbers are widely employed in various fields such as electronics, electrical engineering, mobile communications, aerospace, and automotive industries. However, silicone rubbers are typically challenging to reprocess and degrade. Moreover, with the advancement of technology, higher demands are placed on its thermal conductivity and dielectric properties. In this study, diglycidyl ether terminated polydimethylsiloxane is cured by 4,4′‐dithiodibutyric acid which contains dual dynamic covalent disulfide and ester bonds with triazobicyclodecene as the ester exchange catalyst to prepare silicone rubber vitrimers (SRVs) through a casting method. The SRVs demonstrate a relatively higher intrinsic thermal conductivity of 0.26 W (m⁻1 K⁻1) compared to ≈0.20 W (m⁻1 K⁻1) of conventional silicone rubber. Besides, the SRVs exhibit very low and stable dielectric constant and dielectric loss at both low and high frequencies (X‐band). The lowest dielectric constant and dielectric loss tangent at 10 GHz are 2.75 and 0.0650, respectively. Besides, the dual dynamic covalent bonds enable the SRVs to have excellent reprocessability and fast degradability. Moreover, the SRVs reveal UV‐shielding capability, as the transmittance of the SRVs is 0% from 200 to 400 nm of UV light.

Effects of hexa (ethyl lactate)-cyclotriphosphazene on flame retardancy and mechanical properties of polylactic acid

Using biobased additives to improve the performance of polylactide (PLA) is important for maintaining its sustainability. In this work, an eco-benign flame retardant HELCP was synthesized by reacting ethyl lactate with cyclotriphosphazene. The HELCP was used to modify the flame retardancy of PLA. A small amount of 5.0 wt% HELCP endows PLA with a UL-94 V0 rating and a limiting oxygen index of 25.3 vol%. The mechanical properties and transparency of PLA/HELCP blends is almost the same as neat PLA. Moreover, the molecular weight of PLA blends does not decrease but increase instead. The phosphazene group of HELCP plays an important role in gas phase and the plasticization of HELCP shows a certain melting-away effect which is the flame-retardant mode of action in this system. The ethyl lactate part of HELCP undergoes ester exchange reactions with PLA and improves the compatibility between PLA and HELCP. This work provides a novel method for preparing PLA blends with good flame retardancy and mechanical properties.

Thermadapt Shape Memory PCL-co-PBA Network Exhibiting Tunable Properties and Dynamics of Ester–Ester Exchange Reactions

Thermadapt Shape Memory PCL-<i>co</i>-PBA Network Exhibiting Tunable Properties and Dynamics of Ester–Ester Exchange Reactions

Air-water exchange and risk assessment of phthalic acid esters during the early phase of COVID-19 pandemic in tropical riverine catchments of India

Given the increased load of waste plastic in the solid waste stream after the outbreak of the COVID-19 pandemic, we investigated the fate of selected plastic additives along open burning dumps, industrial and residential transects in tropical riverine catchments of India. Polyurethane foam disk passive air samples, surface water and community stored water (CSW) samples were collected along the Adyar River (AR), Cooum River (CR) and canals in Chennai and Daman Ganga River (DG) in Vapi. Among the quantified phthalic acid esters (PAEs), a widely used plastic additive, di(2-ethylhexyl) phthalate (DEHP), was ubiquitous across all the transects. More open drains and leaching of littered single-use plastic items can be the reason for significantly higher (p < 0.05) levels of PAEs in CR over other rivers with a dominance of di-n-butyl phthalate (DnBP). Prevalence of open burning of dumped plastic waste was the possible primary emission source of PAEs in these riverine catchments. Excluding highly soluble dimethyl phthalate (DMP), air-water exchange processes reflected the secondary emission of all the PAEs from the surface water along the open burning sites. Despite the cleansing effect of the oceanic air mass from the Bay of Bengal and the Indian Ocean, the average atmospheric PAE level was two-fold higher in Chennai than Vapi. Even though Vapi is a coastal city along the Arabian Sea, it was impacted by inland air masses during the sampling event. Open burning dumpsites showed a five-fold increase in atmospheric priority PAEs in Chennai city after the outbreak of the COVID-19 pandemic. DnBP was the major contributor to estrogenicity in CSW and DG, and also posed maximum risk for fishes in the open burning transect of these tropical rivers.

Structural insights on the deformations induced by various mutations on cholesteryl ester transfer protein

Cholesteryl Ester Transfer Protein (CETP) is a plasma glycoprotein that intervenes the reverse cholesterol transport (RCT) by equimolar exchange of Cholesteryl esters (CE) and Triglycerides (TGs) between anti-atherogenic High-Density Lipoproteins (HDLs) and pro-atherogenic Low-Density Lipoproteins (LDLs) resulting in the increased concentration of CEs in LDL. This is a potential cause for the formation of atherosclerotic plaques in blood vessels leading to fatality. Therefore, blocking the function of CETP has emerged as a novel strategy for suppressing atherosclerotic plaques. The crystal structure of CETP revealed two Cholesteryl esters (CEs) in the hydrophobic tunnel and two phospholipids (PLs) plugged on the concave surface. Previous lipid transfer assay experimental studies have shown a substantial reduction in the neutral lipid transfer in [R201S] and [I443W, V198W] mutants. However, the protein conformational arrangements due to the mutations present in the CETP system leading to a decrease in the transfer rate of neutral lipids is not explored. Thus, I explored the reason behind the decreased transfer rate in mutants using molecular dynamics (MD) simulations and free energy calculations. Resulting evidences show that R201S mutant induces unfavorable bending angle to CETP with a decreased binding efficiency between N-terminal phospholipid of CETP with S201. Also, an unfavorable conformation state of TGs is formed which makes them difficult to transfer across CETP. Likewise, [I443W, V198W] mutant induces unfavorable CE, TG, and bending angle conformation to CETP impeding neutral lipid transfer. Thus, my results provide sufficient insights on the causation for a decreased transfer rate as reported earlier. The detailed understanding obtained here could help in developing a new strategy in preventing the function of CETP by blocking the role of potential hot spot residues.

Dielectric‐Breakdown Properties of Ester Oil Prepared from Thermally Degraded Rice Oil

The vegetable‐insulating oils are used in electrical systems recently. Most of vegetable‐insulating oils are manufactured from new oils. In this paper, we propose to develop the insulating oils from the used cooking oil. The used cooking oils that means thermal degraded—vegetable oil has high kinematic viscosity that does not meet the JIS values. In this study, the kinematic viscosity of thermal degraded oil was decreased using ester exchange reaction. We simulated the thermally‐degraded rice ester oil as used cooking oil, and investigated the potential of used cooking oil as insulating oil. We manufactured rice ester oil after thermal degradation before and after the ester‐exchange reaction and measure kinematic viscosity, AC breakdown voltage, moisture amount and volume resistivity for oil samples. We evaluated the degree of thermal degradation of the sample oil using total polar molecule (TPM). The results are described as follows. (1) The kinematic viscosity and volume resistivity of the rice oil increased with the thermal degradation progress (increase in TPM). The kinematic viscosity of the rice ester oil at each TPM value decreased after the ester‐exchange reaction. (2) After vacuum deaeration (2 h at 80°C and 22 h at room temperature), the moisture content of the rice oil before and after the ester‐exchange reaction was almost the same. (3) The AC breakdown strength after ester‐exchange reaction was higher than that of the untreated oil. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.