Super water absorbing and shape memory nanocellulose aerogels from TEMPO-oxidized cellulose nanofibrils via cyclic freezing–thawing

Jiang, Feng; Hsieh, You‐Lo

doi:10.1039/c3ta13629a

Cited by 242 publications

(187 citation statements)

References 51 publications

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“…With the advent of carbon-and bio-based nanober fabrication and controlled assembly, [22][23][24][25][26] super lightweight carbonbased aerogels, super hydrophobic and oleophilic absorbents including those from carbon nanotubes (CNTs), 27 graphene, [28][29][30] CNT-graphene composite, 31 carbonized bacterial cellulose (BC) 32 or carbonaceous nanobers, 33 have been reported to show much higher solvent and oil absorbency ranging from 100-913 g per g, more than one order of magnitude higher than other absorbents. These carbon-based aerogels require complicated and energy-consuming processes to fabricate, and thus are expensive.…”

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confidence: 99%

Amphiphilic superabsorbent cellulose nanofibril aerogels

2014

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Amphiphilic superabsorbent cellulose nanofibril aerogels

2014

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“…19,21,22 These CNCs and CNFs showed intriguing self-assembling behaviors that led to ultrafine fibers 23 and amphiphilic superabsorbent aerogels. 24,25 While chemical approaches generated most homogeneous CNCs and CNFs and excellent CNF yield when combined with mechanical blending from rice straw cellulose, mechanical blending alone usually led to low yields. 17 Considering the merits of mechanical defibrillation, i.e., chemical free and greener processing, nanocellulose quality and yield of nanocellulsoe as well as energy required are among the issues that remain to be resolved.…”

Section: ■ Introductionmentioning

confidence: 99%

Rice Straw Cellulose Nanofibrils via Aqueous Counter Collision and Differential Centrifugation and Their Self-Assembled Structures

Jiang

Kondo

Hsieh

2016

ACS Sustainable Chem. Eng.

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Rice straw cellulose was completely defibrillated via aqueous counter collision (ACC) at a low energy input of 15 kWh/kg, then fractionated by differential centrifugation into four increasing weight fractions of progressively thinner cellulose nanofibrils (CNFs): 6.9% in 80–200 nm, 14.4% in 20–80 nm, 20.3% in 5–20 nm, and 58.4% in less than 5 nm thickness. The 93.1% less than 80 nm or 78.7% less than 20 nm thick CNFs yields were more than double those from wood pulp by other mechanical means but at a lower energy input. The smallest (3.7 nm thick and 5.5 nm wide) CNFs were only a third or less in lateral dimensions than those obatined through ACC processed from wood pulp, bamboo, and microbial cellulose pellicle. The less than 20 nm thick CNFs could self-assemble into continuous submicron (136 nm) wide fibers by freezing and freeze-drying or semitransparent (13–42% optical transmittance) film by ultrafiltration and air-drying with excellent mechanical properties (164 MPa tensile strength, 4 GPa Young’s modulus, and 16% strain at break). ACC defibrillated CNFs retained essentially the same chemical and crystalline structures and thermal stability as the original rice straw cellulose and therefore were much more thermally stable than TEMPO oxidized CNFs and sulfuric acid hydrolyzed cellulose nanocrystals from the same rice straw cellulose.

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“…The solid morphologies from freeze-drying have been shown to be dependent on CNF surface carboxylate contents 1 and concentrations, 20,23 a dispersing medium, 20,28 and freezing-temperatures. 20,24 While highly surface oxidized CNFs associate with each other extensively into more heterogeneous forms of thicker fibers of over 500 nm widths to micrometer wide films, 1 more uniform and finer fibers could only be assembled from CNFs with low surface carboxyl content of 0.59 mmol/g cellulose (125 nm), 1 at extremely low concentration of 0.01 wt % (236 nm wide), 20 or from codispersing in a tert-butanol medium (33−43 nm). 23 As varied surface carboxylation was generated by different extents of oxidation that also affected CNF dimensions, both may have influenced the resulting morphologies.…”

Section: ■ Introductionmentioning

confidence: 99%

Self-assembling of TEMPO Oxidized Cellulose Nanofibrils As Affected by Protonation of Surface Carboxyls and Drying Methods

Jiang

Hsieh

2016

ACS Sustainable Chem. Eng.

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Self-assembling of cellulose nanofibrils (CNFs) as affected by varying extent of protonation on C6 surface carboxyls was investigated under freeze-drying and air-drying processes. Surface carboxyls were protonated from 10.3 to 100%, all on the same TEMPO oxidized and mechanically blended CNFs with identical geometries and level of oxidation. Upon freeze-drying, all CNFs assembled into amphiphilic mass. The mostly charged CNFs assembled into the finest and most uniform fibers (ϕ = 137 nm) that absorbed significantly more nonpolar toluene than water; whereas the fully protonated CNFs assembled extensively into porous and more thermally stable ultrathin filmlike structures that absorbed water and toluene similarly. Ultrafiltration and airdrying induced cyrstallization led to more thermally stable, semitransparent, and hydrophilic films that showed no affinity toward nonpolar toluene. In essence, CNFs could be tuned by varying the degree of surface carboxyl protonation, along with drying processes, to create fibrous to film morphologies, amphiphic to hydrophilic properties, and higher thermal stability. KEYWORDS: Surface carboxyl protonation, Cellulose nanofibrils, Amphiphilic, Hydrophobic, Self-assembly, Thermal stability, TEMPO oxidation ■ INTRODUCTIONThe 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) mediated oxidation of cellulose breaks interfibril hydrogen bonds and converts C6 primary hydroxyls to carboxyls and/or carboxylates depending on the conditions. 1−3 TEMPO-mediated oxidation is among the most investigated defibrillation methods to liberate cellulose nanofibrils (CNFs) and has shown to reduce energy needed for defibrillating cellulose by at least 2 orders of magnitude.3 The defibrillation efficiency can be further aided by mild to moderate mechanical post-treatments that have included magnetic stirring, 4 ) cations could cause hydrogelation via chelation with CNF carboxylate anions 8,9 and protonation of sodium carboxylate to carboxylic acids could induce gelation to pH-responsive CNF hydrogels.10−12 Fully protonated CNFs also have shown to exhibit much better dispersibility in polar aprotic solvents, such as N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), 1,3-dimethyl-2-imidazolidinone (DMI), and 1-methyl-2-pyrrolidone (NMP). 13Protonation of surface carboxyls has also shown to affect the properties of solidified CNFs. Air-dried cast films from fully protonated CNFs showed higher oxygen and hydrogen permeability, 14,15 more resistant to cellulase and soil microorganisms degradation and less water absorbing. 16 The higher gas permeability of fully protonated CNF film was thought to be due to the larger free volume generated from interfibrillar hydrogen bonding, 14 but such speculation has not been confirmed by physical evidence. Thus, how protonation of surface carboxyls on CNFs affects their association into solids during drying has yet to be clearly delineated.Drying nanocellulose into solids is critical to its applications. 20 or from codispersing in ...

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Super water absorbing and shape memory nanocellulose aerogels from TEMPO-oxidized cellulose nanofibrils via cyclic freezing–thawing

Cited by 242 publications

References 51 publications

Amphiphilic superabsorbent cellulose nanofibril aerogels

Amphiphilic superabsorbent cellulose nanofibril aerogels

Rice Straw Cellulose Nanofibrils via Aqueous Counter Collision and Differential Centrifugation and Their Self-Assembled Structures

Self-assembling of TEMPO Oxidized Cellulose Nanofibrils As Affected by Protonation of Surface Carboxyls and Drying Methods

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