Electric Field Alignment of Nanofibrillated Cellulose (NFC) in Silicone Oil: Impact on Electrical Properties

Abstract

This work aims to study how the magnitude, frequency, and duration of an AC electric field affect the orientation of two kinds of nanofibrillated cellulose (NFC) dispersed in silicone oil that differ by their surface charge density and aspect ratio. In both cases, the electric field alignment occurs in two steps: first, the NFC makes a gyratory motion oriented by the electric field; second, NFC interacts with itself to form chains parallel to the electric field lines. It was also observed that NFC chains become thicker and longer when the duration of application of the electric field is increased. In-situ dielectric properties have shown that the dielectric constant of the medium increases in comparison to the randomly dispersed NFC (when no electric field is applied). The optimal parameters of alignment were found to be 5000 Vpp/mm and 10 kHz for a duration of 20 min for both kinds of NFC. The highest increase in dielectric constant was achieved with NFC oxidized for 5 min (NFC-O-5 min) at the optimum conditions mentioned above.

Functional Materials from Nanocellulose: Utilizing Structure–Property Relationships in Bottom‐Up Fabrication

“…Due to their anisotropic diamagnetic susceptibility (arising from the summation of magnetic dipoles of individual bonds within oriented cellulose polymer chains in a CNC), CNCs can be aligned in the presence of external electromagnetic fields. [ 69 ] Although electric field alignment generally leads to highly oriented CNCs (or CNFs [ 70 ] ) in the direction of the applied field, CNCs should be suspended in nonpolar solvents to avoid complications surrounding the high conductivity of water. [ 71–74 ] For magnetic fields however, CNC orientation/ordering depends on the concentration of suspension; for dilute systems, CNCs individually orient in a linear (nematic) fashion with their long axis perpendicular to the applied magnetic field, [ 69 ] for semi‐dilute systems with increased CNC particle–particle interactions, CNCs tend to collectively orient in a nematic fashion in order to minimize translational entropy, [ 75 ] while for concentrated systems, CNCs spontaneously co‐operatively self‐assemble into liquid crystalline (chiral nematic) tactoids with the helical director of the tactoid‐oriented parallel to the applied field (discussed in detail in Section 2.2).…”

A Transparent, Hazy, and Strong Macroscopic Ribbon of Oriented Cellulose Nanofibrils Bearing Poly(ethylene glycol)

“…Although the process for production of individualized CNFs with uniform width and tailored surface properties has been well established during the past decade, the process for the alignment of CNFs into useful materials with both high modulus and specific strength is still a challenge. There has been much effort to fabricate fibers and films with oriented CNFs using techniques such as cold drawing, wet‐extrusion, tape casting, wet‐stretching, and electric field assisted alignment . Especially, a wet‐extrusion process combining hydrodynamic alignment with a dispersion‐gel transition has been recently developed to produce CNFs filaments using a millimeter‐sized flow‐focusing system, a potential route for industrial‐scale production .…”

Cooperative Ordering and Kinetics of Cellulose Nanocrystal Alignment in a Magnetic Field

“…19 Electric field alignment, while effective, requires CNCs to be suspended in nonpolar solvents to avoid complications arising from the high conductivity of water. [20][21][22] Given that CNCs are not colloidally stable in such media, coupled with the fact that organic solvents are discouraged in industrial processing, magnetic alignment may offer a more feasible route to produce controllably aligned CNC materials. [23][24][25] Sugiyama et al were the first to show that the magnetic dipole of individual C-O, C-H, and O-H bonds, and their relative orientations in the cellulose polymer chain, led to a material with anisotropic diamagnetic susceptibility.…”