Free Energy Landscape of Cellulose as a Driving Factor in the Mobility of Adsorbed Water

A mini-review on the dielectric properties of cellulose and nanocellulose-based materials as electronic components

Cellulose-based materials have the advantages of renewable, non-toxic, flexible, and strong mechanical properties, so it of is great significance to study the dielectric properties of cellulose-based materials. In this paper, we summarized the factors influencing the dielectric properties of cellulose and nanocellulose-based dielectric and the ways to change the dielectric properties, mainly exploring the methods to improve the dielectric constant of cellulose-based dielectric materials. Cellulose and nanocellulose-based dielectric need to improve the hygroscopic property, increase the flexibility and reduce dielectric loss of the composite materials. This review summarizes the current state-of-art progress of new dielectric materials for green energy storage and flexible electronic devices.

Entropy drives the adsorption of xyloglucan to cellulose surfaces - A molecular dynamics study

The adsorption of nonionic polymers to cellulose is of large importance both in the plant cell wall during synthesis and for the development of sustainable materials from wood. Here, the thermodynamics of adsorption of the polysaccharide xyloglucan (XG) to both native and chemically modified cellulose with carboxyl groups was investigated using molecular dynamics simulations. The free energy of adsorption was calculated as the potential of mean force between an XG oligomer and model cellulose surfaces in a range of temperatures from 298 K to 360 K. It was found that the adsorption near room temperature is an endothermic process dominated by the entropy of released interfacial water molecules. This was corroborated by quantitative assessment of the absolute entropy per water molecule both at the interface and in the bulk. In the case of native cellulose, the adsorption became exothermic at higher temperatures, while the relatively strong interactions between water and the charged groups of the oxidized cellulose impede such a transition. The results also indicate that the extraction of strongly associated hemicelluloses would be facilitated by low temperature.

Multiscale modelling investigation of wood modification with acetic anhydride

Density functional theory (DFT) and molecular dynamics (MD) simulations were employed to investigate the interaction of cellulose and lignin with acetic anhydride for explaining the wood modification process. Cellulose was modelled with a cellobiose unit and dibenzodioxocin was used to represent the lignin model. Results obtained from both methods revealed that acetic anhydride interacted substantially more with the cellobiose model than the lignin model. The interaction energy of cellobiose-acetic anhydride was higher (about 20 kJ mol-1) than that of lignin-acetic anhydride. DFT results on hydrogen bonding indicated that the hydroxyl group from cellobiose and the aromatic hydroxyl group from lignin models have similar energy values, which explain the equal strength of hydrogen bond interaction. The same trend was also obtained for the substitution of acetyl group in the hydroxyl group. MD results have also predicted that acetic anhydride forms a stronger interaction with cellobiose than with the lignin model, and these findings were in agreement with the DFT results.

Robust Oil-Fouling Resistance of Amorphous Cellulose Surface Underwater: A Wetting Study and Application

The antioil-fouling characteristic of an amorphous cellulose (a-cellulose) surface was elucidated using the sessile droplet method (static) and a modified Wilhelmy plate technique (dynamic). As compared to other hydrophilic surfaces (cellulose acetate, poly(vinyl alcohol), and glass), the oil (poly(dimethylsiloxane)) contact angle on the a-cellulose surface underwater shows the largest value (170.5 ± 5.0°), having the smallest deviation from its theoretical value (180.0°) as estimated by Young's equation. Also, the a-cellulose surface demonstrates the strongest affinity with water in an oil medium (stable hydrophilicity). Moreover, the work of adhesion between the receding oil phase and a-cellulose underwater is quantified to be 10.3 mN/m, approximately one-fourth of that in air (42.0 mN/m). The overall wetting study suggests a rather low oil/solid/water three-phase contact line (TPL) friction in the direction that water displaces oil. A proposed mechanism attributes these phenomena to the water-accessible rigid cellulose chains and supramolecular structure of a-cellulose. The former hinders molecular rearrangement during processing or upon exposure to oil, such that its polar hydroxyl groups are readily accessible to water, thereby retaining its hydrophilicity. The latter allows water to diffuse across the TPL, forming the hydration shells that weaken the van der Waals interactions between oil and cellulose chains. Such findings of the a-cellulose surface can be exploited to fabricate mesh membranes with high water permeation flux (375.4 ± 13.5 L m^-2 h^-1 Pa^-1), high oil/water separation efficiency (93-98%), and long-lasting stability, which is suitable for offshore oil spill remediation.