Preparation and characterization of functionalized cellulose nanocrystals

Boujemaoui, Assya; Mongkhontreerat, Surinthra; Malmström, Eva; Carlmark, Anna

doi:10.1016/j.carbpol.2014.08.110

Cited by 130 publications

(112 citation statements)

References 37 publications

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“…For example, Boujemaoui et al used 2-bromopropionic acid, 3-mercaptopropionic acid, 4-pentenoic acid, and 2-propynoic acid, respectively, to catalyze the hydrolysis of raw cellulose materials. Some active functional groups such as Br-, HS-, alkenyl, and alkynyl were grafted on the surface of CNCs correspondingly, which could be beneficial to further modify CNCs despite the very long reaction time (10 days) [101]. Overall, organic acid hydrolysis is more sustainable and environment-friendly than mineral acid hydrolysis for CNCs production.…”

Section: Organic Acid Hydrolysismentioning

confidence: 99%

Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

Xie

Yang

2018

International Journal of Polymer Science

219

128

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The recent strategies in preparation of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) were described. CNCs and CNFs are two types of nanocelluloses (NCs), and they possess various superior properties, such as large specific surface area, high tensile strength and stiffness, low density, and low thermal expansion coefficient. Due to various applications in biomedical engineering, food, sensor, packaging, and so on, there are many studies conducted on CNCs and CNFs. In this review, various methods of preparation of CNCs and CNFs are summarized, including mechanical, chemical, and biological methods. The methods of pretreatment of cellulose are described in view of the benefits to fibrillation.

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Section: Organic Acid Hydrolysismentioning

confidence: 99%

Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

Xie

Yang

2018

International Journal of Polymer Science

219

128

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“…[26][27][28][29] In addition, atom transfer radical polymerization has been extensively explored to synthesize welldefined polymers on CNC surfaces. [30][31][32][33][34] These grafting from approaches have yielded highly compatible CNCs with contact angles in the range of 62 to 94°; however, the pre-attachment of initiator, polymerization reactions themselves and the work-up/separation are lengthy. To avoid the need for initiator attachment and these reactions which take place in organic solvents, we have demonstrated free radical grafting of vinyl polymers from CNCs in water (using ceric initiation) but the reaction produces very large amounts of homopolymer making separation challenging and the graft densities obtained were low leading to CNC contact angles of only 35-47°.…”

Section: Introductionmentioning

confidence: 99%

One-Pot Water-Based Hydrophobic Surface Modification of Cellulose Nanocrystals Using Plant Polyphenols

Berry

Pelton

et al. 2017

ACS Sustainable Chem. Eng.

200

158

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An environmentally friendly procedure for the surface modification of cellulose nanocrystals (CNCs) in water is presented. Tannic acid (TA), a plant polyphenol, acts as the primer when mixed with CNCs in suspension, which are then reacted with decylamine (DA), the hydrophobe. Schiff base formation/Michael-type addition covalently attaches primary amines with long alkyl tails to CNC-TA, increasing the particle hydrophobicity (contact angle shift from 21° to 74°). After modification, the CNC-TA-DA particles in water phase separate, allowing for easy collection of modified material. The dried product is readily redispersible in toluene and other organic solvents, as demonstrated by turbidity measurements, dynamic light scattering, optical microscopy and liquid crystal self-assembly behavior. Electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, solid-state 13 C NMR, and X-ray diffraction support the successful surface modification and indicate that CNC particle morphology is retained. The modified CNCs have a slightly decreased onset of thermal degradation (ca. 10 °C lower) compared with unmodified CNCs. We believe that this surface modification strategy presents a scalable, simple and green approach to the production of hydrophobic bio-based nanoparticles which may lend themselves as reinforcing agents in nonpolar polymer composites, or stabilizers and rheological modifiers in non-aqueous liquid formulated products.

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“…25 Additionally, it was shown that CNC acid hydrolysis conducted in the presence of only high pKa organic acids required up to 10 days at 100 °C. 20,26 In fact, the majority of concurrent cellulose acid hydrolysis and Fischer esterification reactions have been conducted with organic acids with pKa values ≥ 4.0, thus necessitating the addition of an HCl catalyst or a two-pot process. 23,24 It is well known that total proton concentration is critical for cellulose hydrolysis.…”

Section: Introductionmentioning

confidence: 99%

Concurrent Cellulose Hydrolysis and Esterification to Prepare a Surface-Modified Cellulose Nanocrystal Decorated with Carboxylic Acid Moieties

Spinella

Maiorana

Qian

et al. 2016

ACS Sustainable Chem. Eng.

181

111

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Cellulose nanocrystals (CNCs) were modified with natural di-and tricarboxylic acids using two concurrent acid-catalyzed reactions including hydrolysis of amorphous cellulose segments and Fischer esterification, resulting in the introduction of free carboxylic acid functionality onto CNC surfaces. CNC esterification was characterized by Fourier Transform Infrared Spectroscopy, 13 C solid state magic-angle spinning (MAS) and conductometric titration experiments. Average degree of substitution values for malonate, malate, and citrate CNCs are 0.16, 0.22 and 0.18, respectively. Despite differences in organic acid pKa, optimal HCl cocatalyst concentrations were similar for malonic, malic and citric acids. After isolation of modified CNCs, residual cellulose co-products were identified that are similar to microcrystalline cellulose based on SEM and XRD analysis. As proof of concept, recycling experiments were carried to increase the yield of citrate CNCs. The by-product was then recycled by subsequent citric acid/HCl treatments that resulted in 55% total yield of citrate CNCs.The crystallinity, morphology, and substitution of citrate CNCs from recycled cellulose coproduct is similar to modified citrate CNCs formed in the first reaction cycle. Thermal stability of all modified CNCs under air and nitrogen resulted in T 10% and T 50% values above 256 °C and 323 °C, respectively. Thus, they can be used for melt-processing operations performed at moderately high temperatures without thermal decomposition. Nanocomposites of polyvinyl alcohol with modified CNCs (1 wt% malonate-, malate-, citrate and unmodified CNCs) wereprepared. An increase in the thermal decomposition temperature by almost 40 °C was obtained for PVOH-citrate modified CNC nanocomposites.Furthermore, since TGA determined weight loss up to 150°C is attributed to loss of bound water, this provides a tool to determine CNC water affinity. By 150°C, the weight loss of modified and non-modified CNCs is 6% and 2%, respectively. Consequently, modified CNCs with surface carboxylate groups have higher water affinity than non-modified CNCs. Moreover, significant differences in the thermal stability are observed as a function of the di-or triacid used for CNC modification. Based on the peaks of the derivative thermogravimetric curve (DTG, T 50% ), modified CNCs have the following thermal stability: malonate = HCl > malate > citrate CNCs.Corresponding values for T 50% are 366°C, 365°C, 350°C and 345°C, respectively. The amount of residual char at 600°C for HCl, malonate, malate and citrate CNCs is 8, 13, 16 and 20%, respectively. Hence, it follows that increasing the T 50% for di-and tri-acid modified CNCs results in correspondingly lower char formation. Increased char amounts is likely due to CNC functionalizations that lead to relatively larger number of cross-linking events at elevated temperatures.Since the exclusion of air during melt processing is generally not practical, the effect of CNC modification on thermal stability in air was also determined and the correspo...

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Preparation and characterization of functionalized cellulose nanocrystals

Cited by 130 publications

References 37 publications

Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

One-Pot Water-Based Hydrophobic Surface Modification of Cellulose Nanocrystals Using Plant Polyphenols

Concurrent Cellulose Hydrolysis and Esterification to Prepare a Surface-Modified Cellulose Nanocrystal Decorated with Carboxylic Acid Moieties

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