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Imidazole is reported to be an effective reactant for the production of nanocellulose from hardwood pulp. The morphologies and surface properties of the nanocellulose can be simply tailored according to the water content in the imidazole system: with pure imidazole, cellulose nanofibrils (CNFs) in a yield of 10 wt % can be produced. With 25 wt % of water in imidazole, cellulose nanocrystals (CNCs) are obtained in 20 wt % yield. Both nanocelluloses exhibit crystallinity indices in the order of 70%. Interestingly, they retain the original xylan from the pulp with ca. 9-10 wt % of residual xylan content. [ABSTRACT FROM AUTHOR]

Previous work revealed the possibility of controlling the nanostructuration of maleic anhydride plasma polymer (MAPP) by adjusting the plasma process parameters or adding cellulose nanocrystals (CNCs) previously on the substrate. This work aimed to evaluate the stability of MAPP coating to water drop evaporation. The evaporation process was followed by optical microscopy and the effects of substrate surface chemistry and presence of CNCs were investigated. The presence of CNCs affected not only the MAPP adhesion under wet condition, leading to an impressive morphological reconstruction of MAPP coating, but also the evaporation kinetics. Therefore, this work exhibits a simple way to obtain functional surface patterns by changing the coating wet adhesion and opens new opportunities for the utilization of CNCs. [ABSTRACT FROM AUTHOR]

Lignin-coated cellulose nanocrystals (CNCs) were extracted from the tropical wood Angelim Vermelho in a yield of 47 % based on wood cellulose content. The procedure combined a mild steam explosion process with a treatment using 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]). The resulting CNCs showed exceptional aspect ratios of 83 ± 18 for wood-based CNCs and crystallinity index of 76 %. Residual lignin coating and cellulose acetylation were detected during the procedure and are proposed to minimize the known crystallite thickening. As a result, CNCs in dimensions close to their native state in wood were recovered. Furthermore, this novel extraction of CNCs directly from wood circumvents the tedious purification process necessary for CNC extraction from pulp. [ABSTRACT FROM AUTHOR]

We report for the first time the direct extraction of cellulose nanocrystals (CNCs) from wood by means of a 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) treatment. A native cellulosic product could be recovered in 44% yield with respect to wood cellulose content. The product was analyzed for morphological (TEM, AFM, XRD), chemical (FTIR, 13 C CP/MAS NMR), thermal (DSC, TGA) and surface properties (Zeta potential, contact angle). These analyses evidenced the presence of partially acetylated (surface DS = 0.28) nanocrystals of native cellulose I microstructure, with a crystallinity index of about 75% and aspect ratio of 65. Direct production of CNCs from wood is ascribed to the simultaneous capability of [EMIM][OAc] to (1) dissolve lignin in situ while only swelling cellulose, (2) decrease intermolecular cohesion in wood via acetylation, and (3) to catalyze cellulose hydrolysis. [ABSTRACT FROM AUTHOR]

1Butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO 4 ) is efficient at extracting cellulose nanocrystals from pulp fibers. To shed some light on the respective contributions of swelling and hydrolysis of pulp fibers by [Bmim]HSO 4 , the physical, structural and morphological characteristics of hardwood Kraft pulp fibers were monitored under various conditions of temperature, water content and time. Swelling was largely compounded by hydrolysis at the highest temperatures (120 °C) as evidenced by mass loss and reduced degree of polymerization (DP n ) at this temperature. At 120 °C only, water content appeared to play a significant role on the extent of hydrolysis. At this temperature, a heterogeneous kinetic model involving weak links and amorphous regions best described the experimental data. Hydrolysis rates were maximum at 25% water content in the aqueous ionic liquid. [ABSTRACT FROM AUTHOR]

We report on near theoretical yield production of cellulose I nanocrystals (CNCs) using a two-step hydrolysis with the mildly acidic ionic liquid (IL) 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO 4 ) in aqueous solution from common cellulosic sources. Two successive Taguchi experimental plans were performed to evaluate the impact of selected reaction parameters ( T , t , H 2 O:IL ratio) and their interactions on the CNCs’ yield from bleached softwood kraft pulp (SWP), bleached hardwood kraft pulp (HWP) and microcrystalline cellulose (MCC). With these experimental plans, the molar yield for extraction of nanocrystals was optimized to near theoretical levels, reaching 57.7 ± 3.0%, 57.0 ± 2.0%, and 75.6 ± 3.0%, for SWP, HWP and MCC, respectively. The reaction yields corresponded to a relative crystalline region recovery of 84.1 ± 5.3%, 71.7 ± 1.3%, 76.0 ± 2.0% from SWP, HWP and MCC, respectively. The collected nanocrystals exhibited high aspect ratios (36–43), negligible sulfur content (0.02–0.21%) and high solvent dispersibility in comparison to those obtained with the traditional sulfuric acid method. Additionally these near theoretical yields were achieved for mild reaction conditions with the combined severity factor of 2 and 3 for MCC and pulp, respectively. Overall this two-stage IL-mediated preparation of nanocrystals combines the advantages of achieving high product quality, high reaction yields and mild conditions. [ABSTRACT FROM AUTHOR]

• Carbamation of cellulose nanocrystals with TDI obtained at various surface DS. • Efficiency of grafting different Diels-Alder moieties onto CNCs surface assessed. • Thorough spectroscopy characterization of functionalized CNCs. The Diels-Alder reaction is a promising click chemistry for the design of advanced materials from cellulose nanocrystals (CNCs). Transferring such chemistry to cellulose nanocrystals requires the precise grafting of reactive Diels-Alder moeities under heterogeneous conditions without compromising the nanocrystals morphology. In this study toluene diisocyanate is used as a spacer to graft Diels-Alder moieties viz the furyl and protected maleimido moieties onto cellulose nanocrystals. A factorial experimental design reveals that reaction time and reactant molar ratio positively affect the grafting efficiency, as evidenced by FTIR and CHNS elemental analysis. The surface degree of substitution was analyzed via CHNS elemental analysis and XPS and found to range between 0.05 to 0.30, with a good agreement between the two techniques. 13C CP/MAS NMR confirmed that the grafted moieties and CNCs are intact after reaction. Side reactions were also observed and their impact on performing controllable click chemistry between cellulose nanocrystals is discussed. [ABSTRACT FROM AUTHOR]