Nabin Kumar Karna1, Jakob Wohlert2, Anna Lidén3, Tuve Mattsson4, Hans Theliander5. 1. Division of Forest Products and Chemical Engineering, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Göteborg, Sweden; Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044, Sweden. Electronic address: nabin@chalmers.se. 2. Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044, Sweden; Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, SE-10044, Sweden. Electronic address: jacke@kth.se. 3. Division of Forest Products and Chemical Engineering, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Göteborg, Sweden. Electronic address: annalid@chalmers.se. 4. Division of Forest Products and Chemical Engineering, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Göteborg, Sweden; Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044, Sweden. Electronic address: tuve.mattsson@chalmers.se. 5. Division of Forest Products and Chemical Engineering, Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Kemigården 4, 412 96 Göteborg, Sweden; Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044, Sweden. Electronic address: hanst@chalmers.se.
Abstract
HYPOTHESIS: Interfacial tensions play an important role in dewatering of hydrophilic materials like nanofibrillated cellulose, and are affected by the molecular organization of water at the interface. Application of an electric field influences the orientation of water molecules along the field direction. Hence, it should be possible to alter the interfacial free energies to tune the wettability of cellulose surface through application of an external electric field thus, aiding the dewatering process. SIMULATIONS: Molecular dynamics simulations of cellulose surface in contact with water under the influence of an external electric field have been conducted with GLYCAM-06 forcefield. The effect of variation in electric field intensity and directions on the spreading coefficient has been addressed via orientational preference of water molecules and interfacial free energy analyses. FINDINGS: The application of electric field influences the interfacial free energy difference at the cellulose-water interface. The spreading coefficient increases with the electric field directed parallel to the cellulose-water interface while it decreases in the perpendicular electric field. Variation in interfacial free energies seems to explain the change in contact angle adequately in presence of an electric field. The wettability of cellulose surface can be tuned by the application of an external electric field.
HYPOTHESIS: Interfacial tensions play an important role in dewatering of hydrophilic materials like nanofibrillated cellulose, and are affected by the molecular organization of water at the interface. Application of an electric field influences the orientation of water molecules along the field direction. Hence, it should be possible to alter the interfacial free energies to tune the wettability of cellulose surface through application of an external electric field thus, aiding the dewatering process. SIMULATIONS: Molecular dynamics simulations of cellulose surface in contact with water under the influence of an external electric field have been conducted with GLYCAM-06 forcefield. The effect of variation in electric field intensity and directions on the spreading coefficient has been addressed via orientational preference of water molecules and interfacial free energy analyses. FINDINGS: The application of electric field influences the interfacial free energy difference at the cellulose-water interface. The spreading coefficient increases with the electric field directed parallel to the cellulose-water interface while it decreases in the perpendicular electric field. Variation in interfacial free energies seems to explain the change in contact angle adequately in presence of an electric field. The wettability of cellulose surface can be tuned by the application of an external electric field.
Keywords:
Cellulose-water interface; Free-energy; Molecular dynamics; Potential of mean force; Spreading coefficient; Work of adhesion; Young’s equation