Faiz Ullah Shah

Novel halogen-free chelated orthoborate–phosphonium ionic liquids: synthesis and tribophysical properties

We report on the synthesis, characterisation, and physical and tribological properties of halogen-free ionic liquids based on various chelated orthoborate anions with different phosphonium cations, both without halogen atoms in their structure. Important physical properties of the ILs including glass transition temperatures, density, viscosity and ionic conductivity were measured and are reported here. All of these new halogen-free orthoborate ionic liquids (hf-BILs) are hydrophobic and hydrolytically stable liquids at room temperature. As lubricants, these hf-BILs exhibit considerably better antiwear and friction reducing properties under boundary lubrication conditions for steel-aluminium contacts as compared with fully formulated (15W-50 grade) engine oil. Being halogen free these hf-BILs offer a more environmentally benign alternative to ILs being currently developed for lubricant applications.

Boron in Tribology : From Borates to Ionic Liquids

Boron compounds are widely used in a range of tribological applications such as friction modifiers, antioxidants, antiwear additives, and in many cases as environmentally friendly lubricants. The chemical nature and structure of boron compounds provide multifunctionality. They are used as (1) solid lubricants such as boric acid and hexagonal boron nitride, (2) liquid lubricants such as ionic liquids, (3) lubricant additives such as borate derivatives of various organic and inorganic compounds, and (4) coatings such as cubic boron nitride and different metal borides. Boron is also one of the most favorable elements for coatings and thin films in biotribological and biomedical applications. This review outlines the growing role of boron in lubrication over the past several decades, summarizes the main findings, and identifies future challenges related to boron chemistry.

Atomistic Insight into Orthoborate-Based Ionic Liquids : Force Field Development and Evaluation

We have developed an all-atomistic force field for a new class of halogen-free chelated orthoborate-phosphonium ionic liquids. The force field is based on an AMBER framework with determination of force field parameters for phosphorus and boron atoms, as well as refinement of several available parameters. The bond and angle force constants were adjusted to fit vibration frequency data derived from both experimental measurements and ab initio calculations. The force field parameters for several dihedral angles were obtained by fitting torsion energy profiles deduced from ab initio calculations. To validate the proposed force field parameters, atomistic simulations were performed for 12 ionic liquids consisting of tetraalkylphosphonium cations and chelated orthoborate anions. The predicted densities for neat ionic liquids and the [P6,6,6,14][BOB] sample, with a water content of approximately 2.3-2.5 wt %, are in excellent agreement with available experimental data. The potential energy components of 12 ionic liquids were discussed in detail. The radial distribution functions and spatial distribution functions were analyzed and visualized to probe the microscopic ionic structures of these ionic liquids. There are mainly four high-probability regions of chelated orthoborate anions distributed around tetraalkylphosphonium cations in the first solvation shell, and such probability distribution functions are strongly influenced by the size of anions.

Efficient conversion of lignocellulosic biomass to levulinic acid using acidic ionic liquids

In the present research work, dicationic ionic liquids, containing 1,4-bis(3-methylimidazolium-1-yl) butane ([C4(Mim)2]) cation with counter anions [(2HSO4)(H2SO4)0], [(2HSO4)(H2SO4)2] and [(2HSO4)(H2SO4)4] were synthesised. ILs structures were confirmed using 1H NMR spectroscopy. Thermal stability, Hammett acidity, density and viscosity of ILs were determined. Various types of lignocellulosic biomass such as rubber wood, palm oil frond, bamboo and rice husk were converted into levulinic acid (LA). Among the synthesized ionic liquids, [C4(Mim)2][(2HSO4)(H2SO4)4] showed higher % yield of LA up to 47.52 from bamboo biomass at 110°C for 60min, which is the better yield at low temperature and short time compared to previous reports. Surface morphology, surface functional groups and thermal stability of bamboo before and after conversion into LA were studied using SEM, FTIR and TGA analysis, respectively. This one-pot production of LA from agro-waste will open new opportunity for the conversion of sustainable biomass resources into valuable chemicals.

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

Insights into the effect of CO2 absorption on the ionic mobility of ionic liquids

We investigate a comparative effect of CO2 absorption on the ionic mobility of two choline based ionic liquids comprising two different anions such as threonine and imidazole. The synthesized ionic liquids were characterized using 1H and 13C NMR and other spectroscopic techniques. By keeping a common cation and changing the anion from threonine to imidazole both the viscosity and density reduced drastically. We found that [N1,1,6,2OH][Imi] exhibits the highest CO2 capture capacity at 20 °C of 5.27 mol of CO2 per kg of ionic liquid (1.27 mol of CO2 per mol of ionic liquid, 23.26 wt% of CO2) whereas [N1,1,6,2OH][Threo] exhibits 3.6 mol of CO2 per kg of ionic liquid (1.05 mol of CO2 per mol of ionic liquid, 15.87 wt% of CO2). The activation energy for diffusion is calculated using the Vogel-Fulcher-Tamman (VFT) equation in the form of diffusivity. It was found that the activation energy for the diffusion of [N1,1,6,2OH][Threo] is ∼10 times higher than that of [N1,1,6,2OH][Imi]. 1H diffusion NMR data revealed that the diffusivity of [N1,1,6,2OH][Imi] is increased after CO2 absorption whereas a decrease in diffusivity was observed in the case of [N1,1,6,2OH][Threo]. This anomalous behavior of [N1,1,6,2OH][Imi] was further explained by using DFT calculations.

Solid-state 13C, 15N and 29Si NMR characterization of block copolymers with CO2 capture properties

Natural abundance solid‐state multinuclear (13C, 15N and 29Si) cross‐polarization magic‐angle‐spinning NMR was used to study structures of three block copolymers based on polyamide and dimethylsiloxane and two polyamides, one of which including ferrocene in its structure. Assignment of most of the resonance lines in 13C, 15N and 29Si cross‐polarization magic‐angle‐spinning NMR spectra were suggested. A comparative analysis of 13C isotropic chemical shifts of polyamides with and without ferrocene has revealed a systematic shift towards higher δ ‐values (de‐shielding) explained as the incorporation of paramagnetic ferrocene into the polyamide backbone. In addition, the 13C NMR resonance lines for ferrocene‐based polyamide were significantly broadened, because of paramagnetic effects from ferrocene incorporated in the structure of this polyamide polymer. Single resonance lines with chemical shifts ranging from 88.1 to 91.5 ppm were observed for 15N sites in all of studied polyamide samples. 29Si chemical shifts were found to be around −22.4 ppm in polydimethylsiloxane samples that falls in the range of chemical shifts for alkylsiloxane compounds. The CO2 capture performance of polyamide‐dimethylsiloxane‐based block copolymers was measured as a function of temperature and pressure. The data revealed that these polymeric materials have potential to uptake CO2 (up to 9.6 cm3 g−1) at ambient pressures and in the temperature interval 30–40 °C. Copyright

Plasticizing and crosslinking effects of borate additives on the structure and properties of poly(vinyl acetate)

As an environmentally friendly, low-cost and widely used polymer, poly(vinyl acetate) (PVAc) is worth modifying to achieve better properties. Here, we report on the influence of borate additives on the structure and properties of partially hydrolysed PVAc. In addition to the general crosslinking function of borate additives, an extraordinary plasticizing effect was found. By controlling the pH from 4 to 11 during sample preparation, the plasticizing and crosslinking effects can be shifted. In alkaline conditions, the degree of crosslinking in the PVAc/borate sample is increased; however, this increase declines gradually with an increase in the borate additive content, which impacts the morphology of the PVAc latex particles, as well as the mechanical and thermal properties of the PVAc/borate films. In contrast, in acidic conditions, the PVAc/borate films are plasticized by borate additives; thus, their ultimate mechanical strength, elastic moduli and thermal stabilities decrease, while the water diffusivities increase.

Dynamic Properties of Imidazolium Orthoborate Ionic Liquids Mixed with Polyethylene Glycol Studied by NMR Diffusometry and Impedance Spectroscopy

We used 1H pulsed field gradient nuclear magnetic resonance to study the self‐diffusion of polyethylene glycol (PEG) with average molecular mass of 200 and ions in mixtures of PEG with imidazolium bis(mandelato)borate (BMB) and imidazolium bis(oxalato)borate ionic liquids (ILs). The IL was mixed with PEG in the concentration range of 0–100 wt%. Within the temperature range of 295 to 353 K, the diffusion coefficient of BMB is slower than that of the imidazolium cation. The diffusion coefficients of PEG, as well as the imidazolium cation and BMB anions, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state. Generally, increasing the concentration of PEG leads to an increase in the diffusion coefficients of PEG and both the ions and decreases their activation energy for diffusion. Nuclear magnetic resonance chemical shift alteration analysis showed that the presence of PEG changes the chemical shifts of both ions but in different directions. Impedance spectroscopy was used to measure the ionic conductivity of the ILs mixed with PEG. Copyright

Transport and Association of Ions in Lithium Battery Electrolytes Based on Glycol Ether Mixed with Halogen-Free Orthoborate Ionic Liquid

Ion transport behaviour of halogen-free hybrid electrolytes for lithium-ion batteries based on phosphonium bis(salicylato)borate [P4,4,4,8][BScB] ionic liquid mixed with diethylene glycol dibutyl ether (DEGDBE) is investigated. The Li[BScB] salt is dissolved at different concentrations in the range from 0.15 mol kg−1 to 1.0 mol kg−1 in a mixture of [P4,4,4,8][BScB] and DEGDBE in 1:5 molar ratio. The ion transport properties of the resulting electrolytes are investigated using viscosity, electrical impedance spectroscopy and pulsed-Field Gradient (PFG) NMR. The apparent transfer numbers of ions are calculated from the diffusion coefficients measured by using PFG NMR. PFG NMR data suggested ion association upon addition of Li salt to the [P4,4,4,8][BScB] in DEGDBE solution. This is further confirmed by liquid state 7Li and 11B NMR, and FTIR spectroscopic techniques, which suggest strong interactions between the lithium cation and oxygen atoms of the [BScB]− anion in the hybrid electrolytes.