Coaxial Spinning of All-Cellulose Systems for Enhanced Toughness: Filaments of Oxidized Nanofibrils Sheathed in Cellulose II Regenerated from a Protic Ionic Liquid

Abstract

Hydrogels of TEMPO-oxidized nanocellulose (TO-CNF) were stabilized for dry-jet wet spinning using a shell of cellulose dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium propionate ([DBNH][CO2Et]), a protic ionic liquid (PIL). Coagulation in an acidic water bath resulted in continuous core-shell filaments (CSF) that were tough and flexible: average dry (and wet) toughness of ~11 (2) MJ . m -3 and elongation of ~9 ( 14) %. CSF morphology, chemical composition, thermal stability, crystallinity, and bacterial activity were assessed using scanning electron microscopy with energy dispersive X-ray spectroscopy, liquid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, pyrolysis gas chromatography-mass spectrometry, wide angle X-ray scattering and bacterial cell culturing, respectively. The coaxial wet spinning yields PIL-free systems carrying on the surface the cellulose II polymorph, which not only enhances the toughness of the filaments but facilities their functionalization.apply a strategy based on the principles of the circular economy. Bio-based materials and, in particular, cellulose nanomaterials (CNMs) have become excellent candidates in this regard, as they could partially replace materials based on non-renewable resources. Indeed, CNMs enable high-performance, green functional materials with a broad spectrum of applications, e.g., electronics, biomedical and tissue engineering scaffolds, coatings, food, textiles, and even in daily use goods [1][2][3][4][5][6][7][8] .Cellulose resources have the potential of becoming a platform to develop novel CNMs with high mechanical performance since nanocellulose, in its cellulose I crystalline phase, possess an elastic modulus of about 150 GPa and 18-50GPa in the longitudinal and transverse directions, respectively 9,10 . The regioselective C6 oxidation of nanocellulose fibers can be additionally catalyzed by the use of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) nitroxyl radical to produce hydrogels with high transparency 11 , an extensive degree of fibrillation 12 , and low cytotoxicity 13 . These TEMPO-oxidized cellulose nanofibers (TO-CNF) are suitable for applications in diverse fields such as packaging 3,4,[14][15][16] , textiles [17][18][19][20] , biosensing and bioelectronics 21,22 , fire retardancy 23 , wound dressing and cell delivery [24][25][26] , among others 3 . Despite its excellent mechanical properties, materials derived from nanocellulose and, in particular, TEMPO-oxidized nanocellulose, have several drawbacks inherent to its nature. For instance, these materials are mostly hydrophilic owing to the high concentration of hydroxyl and carboxylate groups; this causes mechanical instability of the formed materials under wet/humid conditions, and exhibit rather low aspect ratios compared to dissolved polymers. The limited aspect ratio makes it difficult to create oriented structures of cellulose nanofibrils by drawing 27,28 . Many attempts to overcome hydrophilicity challenges have been made through appr...

Micro- and nanocelluloses from non-wood waste sources; processes and use in industrial applications

“…50 Furthermore, in a similar dry jet-wet spinning ionic liquid manufacturing process, core shell filaments (CSF) with regenerated cellulose exterior and inner core of CNF have been fabricated from dissolved cellulose and TEMPO oxidized CNF hydrogel. 51 These CSFs have been modified to function in e.g., wearable electronics, adsorbents, flame retardant fibers, and smart textiles. 51 Overall, ionic liquids combined with waste cellulose sources could achieve more sustainable textile and smart textile industries.…”

“…51 These CSFs have been modified to function in e.g., wearable electronics, adsorbents, flame retardant fibers, and smart textiles. 51 Overall, ionic liquids combined with waste cellulose sources could achieve more sustainable textile and smart textile industries.…”

Efficient Swelling and Mercerization of Bagasse Fiber by Freeze-Thaw-Assisted Alkali Treatment

“…The most widely used in the industry is cellulose II, although cellulose I occurs naturally (Yagura et al, 2020) , (Kita et al, 2020). Cellulose II is obtained by dissolution/regeneration (Reyes et al, 2020) or mercerization (Marzouki et al, 2019). Fibers are inflated using sodium hydroxide solution (Öztürk et al, 2006).…”

Nanocellulose Hybrid Lignin Complex Reinforces Cellulose to Form a Strong, Water-Stable Lignin–Cellulose Composite Usable as a Plastic Replacement

“…Improving the fibre orientation by wet stretching and shear orientation enhances the strength of the cellulose sheet, but this requires special equipment, thereby limiting large-scale production [16,17]. Ionic crosslinking can effectively improve the water-stability of cellulose sheets [18,19], but not the mechanical strength. Therefore, many challenges remain in the development of a simple and scalable method to enhance the mechanical strength and water-stability of cellulose.…”