Synthesis and tribological investigation of 4-vinyl guaiacol–based thioether derivatives as multifunctional additives and their interactions with the tribo surface using quantum chemical calculations

Novel 4-vinyl guaiacol based thioether derivatives were synthesized in a three-step reaction procedure by thiol-ene coupling as the key step. The synthesized compounds were characterised by spectroscopic techniques and evaluated for their tribological and antioxidant properties in two different base oils namely epoxy2-ethylhexyl esters of karanja fatty acids (EKE) and dioctyl sebacate (DOS). It was found that the synthesized products were exhibited superior antioxidant performance compared to butylated hydroxytoluene (BHT). All the three synthesized additives were improved the tribological properties of the base oil EKE and DOS. Dithio derivative at 0.75 wt% reduced the wear scar diameter by 36% and at 1 wt% improved the weld point by 33% of base oil EKE. Surface and elemental analysis result suggests that in the tribochemical process the synthesized thioether derivatives decompose and form an effective tribofilms on interacting surfaces. X-ray Photoelectron Spectroscopy (XPS) of the surface lubricated with base oil containing DMFD was evidence for the formation of tribofilm with FeS, FeSO₄ and Fe₂O₃. The antiwear behaviour of the additives was well correlated with quantum chemical calculations. Overall the dithio derivative is more effective as antiwear, extreme pressure and antioxidant bio lubricant additive than other thioether derivatives.     

The increase in diffraction efficiency of an azobenzene side-chain polymer using imidazolium and ammonium ionic liquids

The advancement of the information age has intensified the focus on photosensitive materials for information storage devices. To develop new photosensitive two azobenzene side-chain polymers i.e., poly(E)-3-(4-((4-nitrophenyl)diazenyl)phenoxy)propyl acrylate (polymer-1) and poly(E)-3-(4-((2-methoxy-4-nitrophenyl)diazenyl)phenoxy)propyl acrylate (polymer-2), were developed, and their diffraction efficiency was evaluated. The impact of ionic liquids (ILs) on the diffraction efficiency was evaluated by combining the polymers with imidazolium and ammonium families of ILs such as 1-butyl-3-methylimidazolium bromide [Bmim]Br, 1-ethyl-3-methyl-imidazolium-bromide [Emim]Br (imidazolium ILs), and triethylammonium methanesulfonate [TMEAS] (ammonium IL). The molecular interaction of both azobenzene side-chain polymers with the ILs was evaluated before the diffraction efficiency studies by employing UV–vis, FT-IR, and confocal Raman spectroscopies. The spectroscopic studies revealed the interaction of the polymers with the imidazolium and ammonium ILs. The mean diffraction efficiency of polymers-1 and ?2 were ～0.05 and ～0.022%, respectively. After the addition of the ILs, the diffraction efficiency increased. The highest diffraction efficiency was achieved with the polymer-2 + [Emim]Br system of 3.5% and polymer-2 + TEMS combination of 4.03%. Therefore, although the diffraction efficiency of polymer-1 was higher than that of polymer-2, after adding the ILs, the diffraction efficiency of polymer-2 surpassed that of the polymer-1 + ILs system.     

烷基咪唑螯合硼离子液体的合成及摩擦学性能

以1种环境友好的双水杨酸螯合硼为阴离子中心,以咪唑环为阳离子骨架,合成了7种新的具有不同烷基直链的螯合硼离子液体D-C_nImBScB(n=4,6,8,10)和C_nImC8BScB(n=4,6,10).利用核磁共振波谱(~1H NMR)、热重分析(TGA)和差示扫描热量(DSC)等技术对7种双咪唑螯合硼离子液体进行了结构和热稳定性分析.以聚乙二醇(PEG200)作为基础油,双边咪唑螯合硼离子液体D-C_nImBScB(n=4,6,8,10)和C_nImC8BScB(n=4,6,10)作为添加剂,采用四球摩擦磨损试验机、扫描电子显微镜(SEM)和能量色散X射线光谱仪(EDX)分别对油样的抗磨减摩性能、磨斑形貌和磨斑表面元素分布进行了分析表征.结果表明,D-C_nImBScB(n=4,6,8,10)和C_nImC_8BScB(n=4,6,10)可用作在较宽温度范围使用的润滑油添加剂,添加C_6ImC_8BScB的PEG200油样抗磨效果最佳,其磨斑直径为0.712 mm,与PEG200相比降低了27.49%,通过适当调节阳离子咪唑环骨架上的双边烷基链长度可以调控离子液体的摩擦学性能.     

C60-丙烯酸月桂酯共聚物的合成及其摩擦学行为

合成了一种新颖的油溶性C60-丙烯酸月桂酯共聚物,采用四球摩擦磨损试验机、扫描电子电镜研究了其作为液体石蜡润滑添加剂的摩擦学特性,结果表明,C60-丙烯酸月桂酯共聚物可提高石蜡基础液的抗磨性能,改善微观磨损状态.     

Synthesis of Fullerene-Acrylamide Copolymer Nanoball and Its Lubrication Properties

A novel fuUerene-acrylamide copolymer was synthesized via radical polymerization. It is soluble in polar solvents such as water, dimethyl sulfoxide etc. The product was characterized by FTIR, UV-Vis and GPC. TEM analysis shows that the average particle diameter is about 46 nm. Four-ball tests show that the addition of a certain concentration of the fullerene copolymer to base stock (2 wt% triethanolamine and 0.5 wt% OPZ aqueous solution) can effectively raise the load-carrying capacity (PB value) and the antiwear ability. SEM analysis shows that the addition results in reducing diameter of wear scar and decreasing wear.     

A functionalised ionic liquid: 1-(3-chloro-2-hydroxypropyl)-3-methyl imidazolium chloride

An ionic liquid (IL) containing an appended 3-chloro-2-hydroxypropyl functionality group 1-(3-chloro-2-hydroxypropyl)-3-methyl imidazolium chloride was synthesised by the reaction of N-methyl imidazole, hydrochloric acid and epichlorohydrin. The ionic liquid showed reasonably high conductivity and heat stability up to 230°C. Its structures were characterised by FT-IR, ¹H NMR and ¹³C NMR spectra. The physical characteristics of the ionic liquid, such as conductivity and solvation abilities have been investigated. Due to its high polarity, the IL is able to dissolve many inorganic salts, and due to hydroxyl-rich microenvironment, it is able to dissolve cellulose go up to 10 (wt%). The ILs can be used for synthesising other ILs or polyelectrolyte.     

Study of the Alkyl Chain Length on Laccase Stability and Enzymatic Kinetic with Imidazolium Ionic Liquids

The activity and stability of laccase and their kinetic mechanisms in water soluble ionic liquids (ILs): 1-butyl-3-methyl imidazolium chloride [C₄mim][Cl], 1-octyl-3-methyl imidazolium chloride [C₈mim][Cl], and 1-decyl-3-methyl imidazolium chloride [C₁₀mim][Cl] were investigated. The results show that an IL concentration up to 10% is satisfactory for initial laccase activity at pH 9.0. The laccase stability was well maintained in [C₄mim][Cl] IL when compared to the control. The inactivation of laccase increases with the length of the alkyl chain in the IL: [C₁₀mim][Cl] > [C₈mim][Cl] > [C₄mim][Cl]. The kinetic studies in the presence of ABTS as substrate allowed calculating the Michaelis–Menten parameters. Among the ILs, [C₄mim][Cl] was the suitable choice attending to laccase activity and stability. Alkyl chains in the ions of ILs have a deactivating effect on laccase, which increases strongly with the length of the alkyl chain.     

Understanding the mechanism of cellulose dissolution in 1-butyl-3-methylimidazolium chloride ionic liquid via quantum chemistry calculations and molecular dynamics simulations

While N,N′-dialkylimidazolium ionic liquids (ILs) have been well-established as effective solvents for dissolution and processing of cellulose, the detailed mechanism at the molecular level still remains unclear. In this work, we present a combined quantum chemistry and molecular dynamics simulation study on how the ILs dissolve cellulose. On the basis of calculations on 1-butyl-3-methylimidazolium chloride, one of the most effective ILs dissolving cellulose, we further studied the molecular behavior of cellulose models (i.e. cellulose oligomers with degrees of polymerization n = 2, 4, and 6) in the IL, including the structural features and hydrogen bonding patterns. The collected data indicate that both chloride anions and imidazolium cations of the IL interact with the oligomer via hydrogen bonds. However, the anions occupy the first coordination shell of the oligomer, and the strength and number of hydrogen bonds and the interaction energy between anions and the oligomer are much larger than those between cations and the oligomer. It is observed that the intramolecular hydrogen bond in the oligomer is broken under the combined effect of anions and cations. The present results emphasize that the chloride anions play a critically important role and the imidazolium cations also present a remarkable contribution in the cellulose dissolution. This point of view is different from previous one that only underlines the importance of the chloride anions in the cellulose dissolution. The present results improve our understanding for the cellulose dissolution in imidazolium chloride ILs.     

Functionalized imidazolium wear‐resistant ionic liquid ultrathin films for MEMS/NEMS applications

As a kind of new material, ionic liquids (ILs) are considered a new type of lubricant for micro/nanoelectromechanical system (M/NEMS) due to their excellent thermal and electrical conductivity. However, so far, only a few reports have investigated the friction and wear of thin films of these materials at the micro scale. Evaluating the nanoscale tribological performance of ILs when applied as films of a few nanometers thickness on a substrate is a critical step for their application in M/NEMS devices. To achieve this purpose, IL thin films with four kinds of anions were synthesized and prepared on single‐crystal silicon wafers by the dip‐coating method. Film thickness was determined by the ellipsometric method. Their surface morphologies were observed by means of atomic force microscopy (AFM). The nano and micro tribological properties of the IL films were investigated by a friction force microscope (FFM)with a spherical probe and a UMT‐2MT tribotester, respectively. The corresponding morphologies of the wear tracks of the IL films were examined using a three‐dimensional non‐contact interferometric microscope. The impact of temperature on the adhesion behavior was studied, as well as the effect of sliding frequency and load on the friction coefficient, load bearing capacity and anti‐wear durability. It was found that friction, adhesion and durability of IL films were strongly dependent on their anionic molecular structures, wettability and ambient environment. Copyright © 2010 John Wiley & Sons, Ltd.     

Novel imidazolium‐based poly(ionic liquid)s: preparation,characterization, and absorption of CO2

The development of novel materials for carbon dioxide (CO₂) capture is of great importance in resource utilization and environmental preservation. In this study, imidazolium‐based ionic liquids (ILs) with symmetrical ester and hydroxyl groups were prepared, and their corresponding polymer were synthesized by melt condensation polymerization. The structure and properties of the poly(ionic liquid)s (PILs) were characterized by proton nuclear magnetic resonance, gel permeation chromatograph, differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy. In addition, the CO₂ sorption behavior of the IL monomers and PILs were studied at a low pressure (648.4 mmHg CO₂) and under a temperature of 25°C using a thermogravimetric analyzer. The CO₂ sorption capacity of 1,3‐bis(2‐hydroxyl ethyl)‐imidazolium hexafluorophosphate ([HHIm]PF₆, 10 mol%) was the highest among all the IL monomers and PILs studied. This capacity is also much higher than those reflected of previously reported ILs. Moreover, the sorption equilibrium of [HHIm]PF₆ was achieved within a short time. Copyright © 2011 John Wiley & Sons, Ltd.     

MoS2的水热合成及其润滑性能

利用水热合成法在相对较低的反应温度(200 ℃)和较短的反应时间(24 h)内合成了MoS2.采用透射电子显微镜(TEM)、X射线光电子能谱(XPS)和X射线衍射(XRD)分析了合成的纳米MoS2的结构.同商品MoS2（平均颗粒直径为3～5 μm）进行了摩擦学性能对比，并利用俄歇电子能谱(AES)深度剖析和XPS分析了MoS2作为润滑剂在钢磨损表面的粘着成膜作用及润滑机理.结果表明,该水热合成的产品具有较商品MoS2更低的摩擦系数，适合在大载荷、长时间工作状况下使用.     

A comparison of phosphorus and fluorine containing IL lubricants for steel on aluminium

Ionic liquids have been shown to be highly effective lubricants for a steel on aluminium system. This work shows that the chemistry of the anion and cation are critical in achieving maximum wear protection. The performance of the ILs containing a diphenylphosphate (DPP) anion all showed low wear, as did some of the tris(pentafluoroethyl)trifluorophosphate (FAP) and bis(trifluoromethanesulfonyl)amide (NTf(2)) anion containing ILs. However, in the case of the FAP and NTf(2) based systems, a cation dependence was observed, with relatively poor wear resistance obtained in the case of an imidazolium FAP and two pyrrolidinium NTf(2) salts, probably due to tribocorrosion caused by the fluorine reaction with the aluminium substrate. The systems exhibiting poor performance generally had a lower viscosity, which also impacts on their tribological properties. Those ILs that exhibited low wear were shown to have formed protective tribofilms on the aluminium alloy surface.     

Reversed phase liquid chromatography of alkyl-imidazolium ionic liquids

Eleven 1-alkyl-3-methyl imidazolium ionic liquid (IL) salts were analyzed in reversed phase mode with a Kromasil C18 column. The mobile phases were water-rich acetonitrile solutions (water content > or =70%, v/v) without any added salts. It is shown that it is possible to separate different ILs sharing the same cation and differing by the anion when salt-free mobile phases are used. When a buffer, acetate or phosphate salt, or any salt, such as sodium chloride or sodium tetrafluorobarate, is added to the mobile phase, the ILs differing only by their anions cannot be separated. ILs with different alkyl chains in the imidazolium cation are separated by mobile phases with or without added salts following a hydrophobic interaction behavior: log k is proportional to nC, the carbon number of the alkyl chain. Important differences in ion/stationary phase interactions are observed depending on the ionic content of the mobile phase. With salt-free mobile phases, the IL/C18 stationary phase interactions correspond to concave isotherms associated with fronting peaks for all ILs. With mobile phase containing 0.01 M of salt, tailing IL peaks correspond to convex adsorption isotherms. Also, the IL retention factor depends on the concentration and nature of the added salt. Hexafluorophosphate chaotropic anions can adsorb on the Kromasil C18 surface dramatically increasing the imidazolium cation retention factors.     

咪唑螯合硼离子液体的合成、表征及摩擦学性能

以一类环境友好的螯合硼离子液体为研究对象,合成了4种具有不同烷基直链阳离子中心的螯合硼离子液体C_nMImBScB(n=2,4,6,8);通过核磁共振波谱(NMR)、电耦合等离子体发射光谱(ICP-OES)、热重分析(TGA)和差示扫描量热分析(DSC)等方法对4种螯合硼离子液体进行了结构分析、硼含量测定和热稳定性分析.以聚乙二醇200(PEG200)作为基础油样品,C_nMImBScB(n=2,4,6,8)作为添加剂,采用四球摩擦磨损试验机、扫描电子显微镜(SEM)和能量色散X射线光谱(EDX)分别对油样的减摩抗磨性能、磨斑形貌和磨斑表面元素分布进行了分析和表征.结果表明,C_nMImBScB(n=2,4,6,8)可作为在较宽温度范围内使用的润滑油添加剂,离子液体的低浓度(质量分数1%~2%)添加使PEG200的摩擦性能得到大幅度提高,摩擦系数最大降低58.46%,磨斑直径最大降低20.5%;硼元素沉积到表面参与润滑膜的成膜,磨斑表面碳元素含量的增加也有助于摩擦性能的提高.     

Temperature dependence of the electrical conductivity in EMIM-based ionic liquids: Evidence of Vogel–Tamman–Fulcher behavior

We present measurements of the electrical conductivity versus temperature for six pure 1-ethyl-3-methyl imidazolium (EMIM) based ionic liquids (ILs) at atmospheric pressure. The temperature range measured goes from 250 to 430 K, although the exact range for each IL varies depending on its melting and vaporisation temperatures. The data measured shows that the electrical conductivity value for all ILs, except EMIM-BF₄, increases more than 200 times for temperature increases of 180 K. We have also observed that the temperature dependence of the electrical conductivity for all measured ILs can be fitted with high precision with a Vogel–Tamman–Fulcher (VTF) type equation. From the fitting parameters we will extract the activation energy and the glass transition temperature.     

Optimization of cation structure of imidazolium-based ionic liquids as ionic solvents for rechargeable magnesium batteries

A series of imidazolium cation-based ionic liquids (ILs) have been synthesized and examined as ionic solvents for rechargeable magnesium batteries. The electrolyte solutions consist of these ILs dissolving methylmagnesium bromide with tetrahydrofuran (MeMgBr/THF). The chemical structure of imidazolium cation much influenced the ionic conductivity and the electrochemical window of the system. A reversible process of cathodic deposition and anodic dissolution of magnesium has been successfully achieved at room temperature. The highest value of anodic peak current for magnesium dissolution was obtained in an optimized-structure IL with allyl and methoxyethyl groups as the substituents.     

Synthesis of silica xerogels with highly distinct morphologies in the presence of imidazolium ionic liquids

This article describes the preparation of silica xerogels by the sol–gel technique, using tetraethoxysilane as precursor and hydrofluoric acid as catalyst, in the presence of imidazolium ionic liquids (ILs). The applied ILs 1–3 contained the 1-monoethylene glycol monomethyl ether-3-methylimidazolium cation in combination with the methanesulfonate (1), tetrafluoroborate (2) and hexafluorophosphate (3) anions, respectively. Characterization of these materials was performed by photography, scanning electron microscopy, atomic force microscopy, X-ray diffraction, thermogravimetric analysis and nitrogen adsorption-desorption isotherms. The IL anion was identified as a powerful morphology controller. The methanesulfonate anion of IL 1 induced the formation of a compact lamellar monolith with an interlamellar distance of 1.5 nm and a flat surface. A free flowing powder of aggregated spherical particles was obtained in the presence of tetrafluoroborate IL 2, and the hexafluorophosphate anion of IL 3 induced the formation of porcelain like aggregates with honeycomb shapes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Self‐diffusion and interactions in mixtures of imidazolium bis(mandelato)borate ionic liquids with polyethylene glycol: 1H NMR study

We used ¹H nuclear magnetic resonance pulsed‐field gradient to study the self‐diffusion of polyethylene glycol (PEG) and ions in a mixture of PEG and imidazolium bis(mandelato)borate ionic liquids (ILs) at IL concentrations from 0 to 10 wt% and temperatures from 295 to 370 K. PEG behaves as a solvent for these ILs, allowing observation of separate lines in ¹H NMR spectra assigned to the cation and anion as well as to PEG. The diffusion coefficients of PEG, as well as the imidazolium cation and bis(mandelato)borate (BMB) anion, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state, while the lifetimes of the associated states of the ions and ions with PEG are less than ~30 ms. Generally, increasing the concentration of the IL leads to a decrease in the diffusion coefficients of PEG and both ions. The diffusion coefficient of the anion is less than that of the cation; the molecular mass dependence of diffusion of ions can be described by the Stokes–Einstein model. NMR chemical shift alteration analysis showed that the presence of PEG changes mainly the chemical shifts of protons belonging to imidazole ring of the cation, while chemical shifts of protons of anions and PEG remain unchanged. This demonstrated that the imidazolium cation interacts mainly with PEG, which most probably occurs through the oxygen of PEG and the imidazole ring. The BMB anion does not strongly interact with PEG, but it may be indirectly affected by PEG through interaction with the cation, which directly interacts with PEG. Copyright © 2015 John Wiley & Sons, Ltd.     

(Liquid + liquid) equilibrium for the ternary systems {heptane + toluene + 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide} and {heptane + toluene + 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide} ionic liquids

The (liquid + liquid) equilibrium (LLE) data for two systems containing heptane, toluene, and 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide ([mpim][Tf₂N]) or 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([amim][Tf₂N]) ionic liquids (ILs) were determined at T = 313.2 K and atmospheric pressure. The effect of a double bond in an alkyl side chain in the imidazolium cation was evaluated in terms of selectivity and extractive capacity. The results show a decrease of the amount of toluene and heptane dissolved in the IL with the allyl group. Thus, the distribution ratios of toluene and heptane of [mpim][Tf₂N] IL are higher than those of [amim][Tf₂N] IL. On the other hand, the separation factor of the [amim][Tf₂N] IL increases comparing to [mpim][Tf₂N] IL. The NRTL model was used to correlate satisfactorily the experimental LLE data for the two studied ternary systems.     

Excess molar volumes of binary mixtures (an ionic liquid + water): A review

This review covers recent developments in the area of excess molar volumes for mixtures of {ILs (1) + H₂O (2)} where ILs refers to ionic liquids involving cations: imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium and ammonium groups; and anions: tetraborate, triflate, hydrogensulphate, methylsulphate, ethylsulphate, thiocyanate, dicyanamide, octanate, acetate, nitrate, chloride, bromide, and iodine. The excess molar volumes of aqueous ILs were found to cover a wide range of values for the different ILs (ranging from −1.7 cm³ · mol⁻¹ to 1.2 cm³ · mol⁻¹). The excess molar volumes increased with increasing temperature for all systems studied in this review. The magnitude and in some cases the sign of the excess molar volumes for all the aqueous ILs mixtures, apart from the ammonium ILs, were very dependent on temperature. This was particularly important in the dilute IL concentration region. It was found that the sign and magnitude of the excess molar volumes of aqueous ILs (for ILs with hydrophobic cations), was more dependent on the nature of the anion than on the cation.