Chemical Modification of Reducing End‐Groups in Cellulose Nanocrystals

Heise, Katja; Delepierre, Gwendoline; King, Alistair W. T.; Kostiainen, Mauri A.; Zoppe, Justin Orazio; Weder, Christoph; Kontturi, Eero

doi:10.1002/anie.202002433

Cited by 100 publications

(85 citation statements)

References 190 publications

(491 reference statements)

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“…This property was evidenced by specific staining of the reducing ends or the enzymatic degradation of the non-reducing counterparts (Chanzy & Henrissat, 1985;Hieta, Kuga, & Usuda, 1984). This unique feature of CNCs has motivated a growing, yet still limited, number of research works aiming at regioselectively modifying the reducing end of CNCs, which were recently reported in two reviews (Heise et al, 2020;Tao, Lavoine, Jiang, Tang, & Lin, 2020). Such an asymmetric derivatization of CNCs is highly appealing since it can lead to a variety of innovative behaviors that pave the way to the use of these Janus-like particles in advanced applications.…”

Section: Introductionmentioning

confidence: 99%

RETRACTED: Optimized reducing-end labeling of cellulose nanocrystals: Implication for the structure of microfibril bundles in plant cell walls

Lin

Putaux

Jean

2021

Carbohydrate Polymers

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A strategy to optimize the labeling of the reducing end of native cellulose nanocrystals (CNCs) with gold nanoparticles (AuNPs) was developed and used to investigate the arrangement of the elementary crystallites constituting these biosourced particles. First, CNCs pre-functionalized with thiosemicarbazide molecules were reacted with presynthesized AuNPs. A second method consisted in synthesizing AuNPs in situ from soluble gold derivatives in the presence of CNCs regioselectively functionalized with thiosemicarbazide molecules. Transmission electron microscopy images revealed that the direct reaction resulted in a low labeling yield and the undesired formation of AuNP aggregates. Oppositely, unprecedent high labeling yields were achieved through the in situ growth approach, with a vast majority of CNCs bearing one or several AuNPs on one end. These results evidence that cotton-derived CNCs are composed of the unidirectional assembly of chemically polar elementary crystallites, implying that the acid hydrolysis isolates fragments of microfibril bundles present in the cell walls.

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Section: Introductionmentioning

confidence: 99%

RETRACTED: Optimized reducing-end labeling of cellulose nanocrystals: Implication for the structure of microfibril bundles in plant cell walls

Lin

Putaux

Jean

2021

Carbohydrate Polymers

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“…A wide variety of chemistries and modification routes have been explored. [ 5–7 ]…”

Section: General Characteristics Of Cnmsmentioning

confidence: 99%

Rheological Aspects of Cellulose Nanomaterials: Governing Factors and Emerging Applications

et al. 2021

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of nanomaterials from green, low-cost, abundant, renewable, and biodegradable natural resources. One such attractive bioresource is cellulose, the most abundant biopolymer on earth, which is widely present in various forms of renewable biomass, such as trees, plants, tunicates, and bacteria.Structurally, cellulose is a linear, high molecular weight polysaccharide with repeating glucose units linked by 1-4 glycosidic bonds. Owing to the presence of hydroxyl groups, those linear chains of glucose units link together through van der Waals forces and intermolecular hydrogen bonding to form elementary fibrils, which are further packed into larger aggregates known as microfibrils. [3] Cellulose fibrils consist of disordered (amorphous) regions and highly ordered (crystalline) regions. In the crystalline regions, cellulose chains are closely packed together in highly ordered fashion (parallel to the direction of fibril length), dictated by the intricate intraand intermolecular hydrogen bonding; whereas in the amorphous regions, cellulose chain stacking is less ordered and not as closely packed. Therefore, the amorphous regions are more vulnerable to both physical disintegration and chemical hydrolysis in comparison with crystalline regions. When cellulose is prepared in nano-scale fibrillar or crystalline forms, it is broadly referred to as cellulose nanomaterials (CNMs).The isolation, characterization, modification, and application of CNMs are currently receiving much attention. Understanding Cellulose nanomaterials (CNMs), mainly including nanofibrillated cellulose (NFC) and cellulose nanocrystals (CNCs), have attained enormous interest due to their sustainability, biodegradability, biocompatibility, nanoscale dimensions, large surface area, facile modification of surface chemistry, as well as unique optical, mechanical, and rheological performance. One of the most fascinating properties of CNMs is their aqueous suspension rheology, i.e., CNMs helping create viscous suspensions with the formation of percolation networks and chemical interactions (e.g., van der Waals forces, hydrogen bonding, electrostatic attraction/repulsion, and hydrophobic attraction). Under continuous shearing, CNMs in an aqueous suspension can align along the flow direction, producing shear-thinning behavior. At rest, CNM suspensions regain some of their initial structure immediately, allowing rapid recovery of rheological properties. These unique flow features enable CNMs to serve as rheological modifiers in a wide range of fluid-based applications. Herein, the dependence of the rheology of CNM suspensions on test protocols, CNM inherent properties, suspension environments, and postprocessing is systematically described. A critical overview of the recent progress on fluid applications of CNMs as rheology modifiers in some emerging industrial sectors is presented as well. Future perspectives in the field are outlined to guide further research and development in using CNMs as the next generation rheological modifiers.

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“… 34 As the equilibrium between the cyclic hemiacetals and the open chain aldehydes in CNC REGs is heavily biased toward the hemiacetals, the fraction of reactive (free) aldehydes is very low under aqueous conditions, where these species exist only as transient states. 12 Therefore, the number of functionalities that can possibly be introduced at the chain ends, under realistic conditions, may be very small compared to the overall number of anhydroglucose units (AGUs) present in a CNC. This complicates the analysis of their modification using the standard analytical methods such as IR spectroscopy, solid-state NMR spectroscopy, and elemental analysis.…”

Section: Introductionmentioning

confidence: 99%

“…This complicates the analysis of their modification using the standard analytical methods such as IR spectroscopy, solid-state NMR spectroscopy, and elemental analysis. 12 So far, most reports quoting REG modification have relied on direct analysis using microscopy or on qualitative changes in the colloidal self-assembly characteristics, which cannot quantify the REG-modification and cannot rule out adsorption of reactants on the surface of the CNCs instead of genuine covalent modification. So far, only Heise et al 21 has provided direct spectroscopic evidence of REG modification.…”

Section: Introductionmentioning

confidence: 99%

“…CNCs with end-tethered polymer chains display very different characteristics than uniformly modified CNCs. 12 Their self-assembly behavior is thought to be particularly useful to create ordered materials with defined structural hierarchies, including assemblies on surfaces and in nanocomposite materials. Two methods can be used to graft a polymer at the CNC REGs, that is, grafting onto and grafting from , although steric hindrance is often encountered while utilizing the first approach, whereas grafting from has, in general, the advantage of well-controlled polymer graft lengths and high polymer tether grafting density.…”

Section: Introductionmentioning

confidence: 99%

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Challenges in Synthesis and Analysis of Asymmetrically Grafted Cellulose Nanocrystals via Atom Transfer Radical Polymerization

et al. 2021

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When cellulose nanocrystals (CNCs) are isolated from cellulose microfibrils, the parallel arrangement of the cellulose chains in the crystalline domains is retained so that all reducing end-groups (REGs) point to one crystallite end. This permits the selective chemical modification of one end of the CNCs. In this study, two reaction pathways are compared to selectively attach atom-transfer radical polymerization (ATRP) initiators to the REGs of CNCs, using reductive amination. This modification further enabled the site-specific grafting of the anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS) from the CNCs. Different analytical methods, including colorimetry and solution-state NMR analysis, were combined to confirm the REG-modification with ATRP-initiators and PSS. The achieved grafting yield was low due to either a limited conversion of the CNC REGs or side reactions on the polymerization initiator during the reductive amination. The end-tethered CNCs were easy to redisperse in water after freeze-drying, and the shear birefringence of colloidal suspensions is maintained after this process.

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Chemical Modification of Reducing End‐Groups in Cellulose Nanocrystals

Cited by 100 publications

References 190 publications

RETRACTED: Optimized reducing-end labeling of cellulose nanocrystals: Implication for the structure of microfibril bundles in plant cell walls

RETRACTED: Optimized reducing-end labeling of cellulose nanocrystals: Implication for the structure of microfibril bundles in plant cell walls

Rheological Aspects of Cellulose Nanomaterials: Governing Factors and Emerging Applications

Challenges in Synthesis and Analysis of Asymmetrically Grafted Cellulose Nanocrystals via Atom Transfer Radical Polymerization

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