Anionically Stabilized Cellulose Nanofibrils through Succinylation Pretreatment in Urea–Lithium Chloride Deep Eutectic Solvent

Abstract

Deep eutectic solvents (DESs) are green chemicals that have the potential to replace traditional solvents in chemical reactions. In this study, urea-LiCl DES was used successfully as a reaction medium in the anionic functionalization of wood cellulose with succinic anhydride. The effects of reaction temperature and time on the carboxyl content and yield were evaluated. The analyses of the degree of polymerization and crystallinity revealed that the DES was a nondegrading and nondissolving reaction medium. Three samples with the highest carboxyl contents were further nanofibrillated with a microfluidizer to diameters of 2-7 nm, as observed by atomic force microscopy. Samples treated at 70-80 °C for 2 h gave the best outcome and resulted in highly viscose and transparent gels. The sample treated at 90 °C contained larger nanoparticles and larger aggregates owing to the occurrence of possible side reactions but resulted in better thermal stability.

Anionic wood nanofibers produced from unbleached mechanical pulp by highly efficient chemical modification

“…31 Interestingly, in the current study, the carboxylic acid content of the dissolving pulp was higher than with a previously reported DES based on urea and lithium chloride, even though a succinic anhydride loading over 12 times lower was used. 15 The higher reaction efficiency might be due to the catalytic effect of imidazole. 32 It has been proposed that the reaction between imidazole and anhydrides forms N-acylimidazole, which functions as an intermediate.…”

“…DESs have been used in nanoparticle fabrication [9][10][11] and recently in nanocellulose fabrication. [12][13][14][15] In this study, a DES based on imidazole and triethylmethylammonium chloride (TEMACl) was used as a reaction medium for the chemical modification of nonbleached mechanical pulp (groundwood pulp, GWP). Succinic anhydride was chosen as a reagent, as it allows the production of carboxylated wood material through the formation of a halfester of succinic acid.…”

Efficient Cleavage of Lignin–Carbohydrate Complexes and Ultrafast Extraction of Lignin Oligomers from Wood Biomass by Microwave‐Assisted Treatment with Deep Eutectic Solvent

“…Sirviö et al. showed that acidic DESs can be hydrolytic media for lignocellulose pretreatment and produce cellulose nanocrystals 36, 42, 43. Xu et al.…”

Mechanical fabrication of high-strength and redispersible wood nanofibers from unbleached groundwood pulp

“…The most effective methods for cellulose nanofiber production have so far been based on the use of chemical (Saito et al 2007;Liimatainen et al 2012Liimatainen et al , 2013b or solvent (Selkälä et al 2016) pretreatments for the surface functionalization of bleached pulp fibers. Chemical functionalization involves many drawbacks compared to the use of fibers in their native state, considering the high cost of chemicals, their toxicity, and the difficulties of both recycling (Kuutti et al 2016) and regenerating them (Liimatainen et al 2013a).…”