The solids choline chloride and urea, mixed in a 1 : 2 molar proportion, form the iconic deep eutectic solvent "Reline". A combination of computational and vibrational spectroscopy tools, including inelastic neutron scattering (INS), have been used to probe intermolecular interactions in the eutectic mixture. Reline's experimental spectra were estimated using discrete and periodic ab initio calculations of a molecular aggregate with two choline chloride and four urea units. This is the minimum size required to achieve satisfactory agreement with experiment, as smaller clusters cannot represent all of reline's significant intermolecular interactions. The INS spectrum of reline, compared with that of pure choline chloride, reveals a displacement of chloride anions away from their preferred positions on top of choline's methyl groups, whose torsional movement becomes less hindered in the mixture. Urea, which adopts a planar (sp) shape in the crystal, becomes non-planar (sp) in reline, a feature herein discussed for the first time. In reline, urea molecules form a wide range of hydrogen bonds, from soft contacts to stronger associations, the latter being responsible for the deviation from ideality. The chloride's interactions with choline are largely conserved at the hydroxyl end while becoming weaker at the cationic headgroup. The interplay of soft and strong interactions confers flexibility to the newly formed hydrogen-bond network and allows the ensemble to remain liquid at room temperature.

The solubilities of lignin monomeric model compounds and technical lignins (organosolv and kraft) in aqueous solutions of several deep eutectic solvents (DES) were here investigated. The effects of DES components, temperature and concentration, were evaluated. The results show aqueous solutions of DES to be a new class of powerful solvents where both the hydrogen bond donor and the hydrogen bond acceptor synergistically contribute to increase the solubility of the lignin model compounds, being the dispersive interactions with lignin the driving force behind the good performance of DES. The solubility of the model compounds is shown to be a good guide for the selection of the best DES for technical lignins solubility, leading to identifying an aqueous solution of DES allowing a solubility enhancement of 1181.7 ± 29.2 and 228.5 ± 9.7 times for kraft and organosolv lignin, respectively. The results indicate that the solubility of the technical lignins and their monomers in DES aqueous solutions is driven by a hydrotropic mechanism, here confirmed by dynamic light scattering that is here observed for the first time with DES as hydrotropes.

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Ecopolyol production from acid liquefaction of cork powder was studied for the first time using PEG 400 and glycerol as liquefaction solvents in the presence of sulfuric acid at moderate temperature and atmospheric pressure. The effect of the temperature, concentration of catalyst, and time on the liquefaction yield has been investigated using a fixed set of reaction conditions namely, a liquefaction solvent mixture/cork powder ratio of 5/1 and a solvent mixture PEG 400/glycerol ratio of 90/10. The full-factorial design of experiments (DOE) 23 was applied to obtain an optimized set of liquefaction conditions aiming at minimizing the residue content. The minimum residue contents experimentally obtained in this study were 29 wt %, related to cork powder, which were achieved at 150 °C, 4 wt % of sulfuric acid, and 60 min. This value corresponds to 5 wt % of residue per total mass of reaction product. The polyols obtained under optimal conditions present similar characteristics (hydroxyl number value 219 mgKOH/gpolyol and viscosity 2875 cP, at 25 °C) to those of petroleum-based polyols typically used in the polyurethane foam industry.