Nanostructural Properties and Twist Periodicity of Cellulose Nanofibrils with Variable Charge Density

Abstract

Cellulose nanofibrils (CNFs) are a renewable and facile to produce nanomaterial that recently gained a lot of attention in soft material research. The nanostructural properties of the fibrils largely determine their self-organizing functionalities, and the ability to tune the CNF nanostructure through control of the processing parameters is therefore crucial for developing new applications. In this study, we systematically altered the CNF production parameters (i.e., variation in cellulose source, chemical, and mechanical treatment) to observe their impact on the nanostructural properties of the resulting fibrils. Atomic force microscopy (AFM) allowed detailed topological examination of individual CNFs to elucidate fibril properties such as contour length, kink distribution and the right-handed twist periodicity of individual fibrils. Statistical analysis revealed a large dependency of the fibril properties on the industrial treatment of the cellulose source material. Our results furthermore confirm that the average charge density of the fibrils regulates both contour length and twist periodicity and, thus, has a very strong impact on the final morphology of CNFs. These results provide a route to tune the detailed nanostructure of CNFs with potential impact on the self-organization of these biological colloids and their optimal use in new nanomaterials.

A novel supra coarse-grained model for cellulose

“…The right-hand twist of cellulose was observed and discussed in many experimental and simulation studies (Matthews et al 2006;Conley et al 2016;Paajanen et al 2019;Paavilainen et al 2011;Zhao et al 2013;Hadden et al 2013;Hanley et al 1997;Arcari et al 2019). Although the twist can be clearly seen in TEM (Conley et al 2016) and AFM (Hanley et al 1997;Arcari et al 2019) pictures, it is difficult to deduce exactly how much is the twist per length of fibril. In this respect molecular simulations can be a valuable tool to determine the twist of a CNC.…”

Irregular and suppressed elastic deformation by a structural twist in cellulose nanofibre models

“…In addition, the 14-round twist model is the upper limit length that can be calculated in our system, and the calculations did not converge at lengths longer than that because of the large displacements. The actual CNF can be approximated by the CT ON -CC ON model, and depending on the crystal thickness, surface conditions or drying conditions, it approaches the torsion-free CT OFF -CC OFF model 14,15 . The twisted CNF models were www.nature.com/scientificreports/ www.nature.com/scientificreports/ found to be closer to the linear response material owing to averaging of the nonlinear curvature caused by the anisotropy of the properties.…”

“…In these materials, the CNFs have been assumed to be ideal elastic rods based on their fibrous shapes, and composite theories for a cylindrical elastic rod have often been applied 5,11 . However, a single CNF has recently been demonstrated to have a right-handed twist structure through high-resolution microscopic analyses [12][13][14] . It is not clear whether the twisted fibres exhibit the ideal and regular elastic behaviour.…”

“…Wooden CNFs with a thickness of 2-3 nm obtained by nanofibrillation of wood cell walls have a "righthanded twist" 12 . The twisted CNFs have a torsional period of ~ 232 nm 13 , and the period tends to shorten as the surface charge density increases 14 . A feature of the twisted CNF is that the crystal c axis is itself twisted 15 , which is fundamentally different from macroscopic architectures, such as stone pillars and buildings, in which only the contour shape is arranged in a twisted shape, or the coil springs, in which the twisting axis is not aligned with the centre of coil component.…”

Mechanical Properties Tailoring of 3D Printed Photoresponsive Nanocellulose Composites

“…Samples were prepared according to the procedure used in. [ 27 ] CNC and cin‐CNC were dispersed in water with a concentration of 2 mg L −1 and deposited on freshly cleaved mica for 30 s. Positive surface charge of the mica was previously obtained by pouring a 20 µL drop of 0.05 vol% of (3‐aminopropyl)triethoxysilane (APTES) for 60 s, rinsed with MilliQ water and dried with pressurized air. The samples were stored under vacuum in a desiccator to avoid contamination prior to measurements.…”