A shift towards an economically viable biomass biorefinery concept requires the use of all biomass fractions (cellulose, hemicellulose, and lignin) for the production of high added-value products. As lignin is often underutilized, the establishment of lignin valorization routes is highly important. In-house produced organosolv as well as commercial Kraft lignin were used in this study. The aim of the current work was to make a comparative study of thermoplastic biomaterials from two different types of lignins. Native lignins were alkylate with two different alkyl iodides to produce ether-functionalized lignins. Successful etherification was verified by FT-IR spectroscopy, changes in the molecular weight of lignin, as well as ¹³C and ¹H Nuclear Magnetic Resonance (NMR). The thermal stability of etherified lignin samples was considerably improved with the T_2% of organosolv to increase from 143 °C to up to 213 °C and of Kraft lignin from 133 °C to up to 168 °C, and glass transition temperature was observed. The present study shows that etherification of both organosolv and Kraft lignin with alkyl halides can produce lignin thermoplastic biomaterials with low glass transition temperature. The length of the alkyl chain affects thermal stability as well as other thermal properties.

CO₂ absorption and ion mobility are investigated in a series of 50/50 wt% aqueous solutions of choline-based ionic liquids with different cations and anions: [N_1,1,4,2OH][Threo], [N_1,1,5,2OH][Threo], [N_1,1,6,2OH][Threo], [N1,1,5,2OH][β-ala] and [N_1,1,5,2OH][Tau]. The process of CO2 absorption was completed in an hour reaching maximum of absorption capacity 0.07–0.10 wt% to ionic liquid (by 0.4–0.6 molar ratios). A rapid CO₂ absorption is observed by the formation of solid product as a result of reaction between CO₂ molecule and the ionic liquid. Diffusion coefficients of the cation and anion in the mixture are comparable while the diffusivity of water molecules is found to be quite different from the ions. In the process of CO₂ absorption, an increase in the diffusivity of ions is observed due to the precipitation of solid products and depletion of ions contents in the liquid phase of the system. ¹³C NMR measurements of diffusivity of CO₂ enriched with ¹³C isotope showed that a part of the absorbed CO₂ remained in the liquid phase being physically and chemically bound to ions. The ionic liquid is re-cycled by evaporating water and releasing CO₂ molecules using vacuum and temperature.

We used 1H pulsed field gradient (PFG) NMR 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 (BOB) ionic liquids (ILs). The ionic liquid 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. NMR 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 ionic liquids mixed with PEG.

Thermal stability of different choline based amino acid ionic liquids were studied. Both short term as well as long term thermal studies were carried out. Long term thermal studies of all ILs were carried out by isothermal TGA and short term thermal studies were measured by temperature ramped TGA. Isothermal TGA were studied at two different temperatures 100 °C and 150 °C for 500 min. Whereas, short term thermal stability represents as T_2%, T_5% and T_10% which are the temperature at which 2%, 5% and 10% mass loss of ILs were observed. The effect of alkyl side chain on the cation, etherification of the cation as well structural variation of anion on the thermal stability of choline based ILs were investigated. It was observed that thermal characteristics of ILs towards temperature ramped TGA were different compared to isothermal TGA.

Amino acid ionic liquids (ILs) are the most interesting and effective for CO2 capture due to their low toxicity, biodegradability and fast reactivity towards CO2. Ionic nature of amino acid ILs can raise an environmental issue if the cation counterpart becomes toxic to the aquatic ecosystems and can become potential atmospheric pollutant. In this regard, choline based ILs are known to be promising scaffolds for the development of less toxic amino acid ILs. However, the existing choline amino acid ILs are highly viscous limiting their applicability as solvents. Ether functionalized choline based amino acid ILs with novel series of less toxic green ILs were explored with reduced viscosity and high CO2 capture capacity. A simple, economic, clean and environmentally benign method was utilized for the synthesis of novel choline based amino acid ILs using a commercially available and economical starting material 2-(dimethylamino)ethanol (deanol, a human dietary food supplement). Reported ILs have low viscosity with high CO2 capture capacity (1.62 mol of CO2 /mol of IL, 4.31 mol of CO2/kg of IL, 19.02 wt.% of CO2). Mechanism of [N1,1,6,2O4][Lys]+CO2 reaction and adduct structure was proposed by means of DFT and NMR.

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 [N_1,1,6,2OH][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 [N_1,1,6,2OH][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 [N_1,1,6,2OH][Threo] is ∼10 times higher than that of [N_1,1,6,2OH][Imi]. ¹H diffusion NMR data revealed that the diffusivity of [N_1,1,6,2OH][Imi] is increased after CO₂ absorption whereas a decrease in diffusivity was observed in the case of [N_1,1,6,2OH][Threo]. This anomalous behavior of [N_1,1,6,2OH][Imi] was further explained by using DFT calculations.