The behavior of poplar wood and its components in water‐ethanol mixtures is investigated through a coupled experimental and theoretical approach including physico‐chemical and dynamic mechanical analyses and molecular dynamics simulations. Affinity for water‐ethanol vapors, measured by isothermal gravimetric sorption experiments, features a maximum for mixed vapors. The longitudinal viscoelastic behavior of the same wood upon immersion in ethanol‐water solutions, measured by dynamic mechanical analysis, features a minimum in storage modulus and a maximum damping upon immersion in solutions of intermediate composition. Optical microscopy observation of solvent‐saturated samples evidences inter‐ and intra‐cellular disbonding in pure ethanol and ethanol aqueous solutions. Molecular dynamics simulations provide information on interactions of water‐ethanol solutions with models of cellulose microfibers and lignin. The relative solvation of cellulose microfibers by water and ethanol shows a nearly linear variation with the composition of the solution. In contrast, the accessibility of lignin dimers to the solvent presents a maximum at intermediate ethanol concentrations, in correspondence with a conformational transition of the dimer towards an extended conformation. The modelization of the interactions of cellulose and lignin in water‐ethanol solutions indicates a minimum of adhesion of the two components of wood in the presence of solutions with intermediate concentrations.

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Several silicon nanoclusters (Si n , with n in the range 1−96) electronic and charge states are calculated using sophisticated compound methods, such as G1−G4, CBS, and W1, as well as using a flavor of density functional theory with a variety of basis sets. Results are compared with very precise experimental data when available. The B3PW91 hybrid functional yields results of comparable quality with all compound procedures, especially for bond energies, which systematically improve as the size of the basis set is increased. For the very small clusters, we used basis sets containing up to 131 basis functions per Si, which included up to two sets of hfunctions. All ionization potentials, electron affinities, and dissociation energies are in good agreement with the experimental results. We perform calculations of the biggest clusters, up to Si 96 , using B3PW91/6-31G(d). We calculate second derivatives and thus the vibrational spectra for all clusters, and we generate harmonic force fields for molecular dynamics calculations with these nanoclusters.

Understanding and controlling the physical adsorption of lignin compounds on cellulose pulp is a key parameter for a successful optimization of organosolv processes. The effect of binary organic-aqueous solvents on the coordination of lignin to cellulose was studied with molecular dynamics simulations, considering ethanol and acetonitrile as organic co-solvents in aqueous solutions in comparison to their mono-component counterparts. The structures of the solvation shells around cellulose and lignin, as well as the energetics of the lignin-cellulose adhesion, indicate a more effective disruption of lignin-cellulose binding by binary solvents. The synergic effect between solvent components is explained by their preferential interactions with celluloselignin complexes. In the presence of pure water, long-lasting H-bonds in the lignin-cellulose complex are observed, promoted by the non-favorable interactions of lignin with water. Ethanol and acetonitrile compete with water and lignin for cellulose oxygen binding sites, causing a non-linear decrease of the cellulose-lignin interactions with the amount of the organic component. This effect is modulated by the water exclusion from the cellulose solvation shell by the organic solvent component. The amount and rate of water exclusion depend on the type of organic cosolvent and its concentration.