The rheological properties of natural polymer solutions are difficult to be modeled universally because of the strongly nonlinear relations between viscosities and the external factors and the discreteness of the rheological data owning to different molecular parameters including the molecular weights and size of clusters from different types of natural polymers and solvents. In this study, a typical natural polymer-lignin was selected and dissolved in polyethylene glycol (PEG). The rheological properties of different PEG-lignin solutions (PEG-Ls) and the molecular parameters of the pretreated lignin were tested. Subsequently, machine learning was applied to establish the generalized models considering the molecular parameters. The models were successfully developed in Newtonian and non-Newtonian regimes for PEG-Ls with correlation coefficients of 0.982 and 0.980, respectively. The models and relevant methodology can provide scenarios for further application of natural polymer solutions.

In this study, a new electrolyte system consisting of tetrabutylphosphonium 4-(methoxycarbonyl) phenol ([P4444][4-MF-PhO]) ionic liquid and acetonitrile (AcN) was developed as CO2 electroreduction electrolyte to produce oxalate, and the mechanism was studied. The results showed that using the new ionic liquid-based electrolyte, the reduction system exhibits 93.8% Faradaic efficiency and 12.6 mA cm-2 partial current density of oxalate at -2.6 V (vs. Ag/Ag+). The formation rate of oxalate is 234.4 μmol cm-2 h-1, which is better than that reported in the literature. The mechanism study using density functional theory (DFT) calculation revealed for the first time that [P4444][4-MF-PhO] IL can effectively activate CO2 molecules through ester and phenoxy double active sites, stabilize the reaction intermediate. The potential barriers of the key intermediates *CO2- and *C2O42- formation by induced electric-field was reduced in the phosphonium-based ionic environment, which greatly facilitates the activation and conversion of CO2 molecules to oxalate.

In this work, the excess Gibbs free energy models, i.e., non-random two-liquid (NRTL) model, electrolyte NRTL model, and electrolyte NRTL model including new strategies (association or hydration), were used to describe the macroscale properties and interpret the microstructure, clarifying the role of association and hydration in model development, and the enthalpy of mixing of three imidazolium-based IL-H2O systems containing the same cation but different sizes of anions, i.e., Cl−, Br−, and I− were measured for the first time to provide systematic data for model development. The models were developed and evaluated based on the newly measured data and the osmotic coefficient from the literature. The model reflecting the intrinsic mechanism of dissociation and hydration competition gives the best modeling results. The real ionic strength predicted from the identified model was quantitatively correlated with the electrical conductivities.