Naturally derived cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) are emerging nanomaterials that display high strength, high surface area, and tunable surface chemistry, allowing for controlled interactions with polymers, nanoparticles, small molecules, and biological materials. Industrial production of nanocelluloses is increasing rapidly with several companies already producing on the tons-per-day scale, intensifying the quest for viable products across many sectors. While the hydrophilicity of the nanocellulose interface has posed a challenge to the use of CNCs and CNFs as reinforcing agents in conventional plastics, it is a significant benefit for creating reinforced or structured hydrogel composites (or, when dried, aerogels) exhibiting both mechanical reinforcement and a host of other desirable properties. In this context, this Review describes the quickly growing field of hydrogels and aerogels incorporating nanocelluloses; over 200 references are summarized in comprehensive tables ...

http://pubs.acs.org/doi/pdf/10.1021/acs.chemmater.7b00531

Review of Hydrogels and Aerogels Containing Nanocellulose

Small Angle Scattering of X-Rays

There is an emerging quest for lightweight materials with excellent mechanical properties and economic production, while still being sustainable and functionalizable. They could form the basis of the future bioeconomy for energy and material efficiency. Cellulose has long been recognized as an abundant polymer. Modified celluloses were, in fact, among the first polymers used in technical applications; however, they were later replaced by petroleum-based synthetic polymers. Currently, there is a resurgence of interest to utilize renewable resources, where cellulose is foreseen to make again a major impact, this time in the development of advanced materials. This is because of its availability and properties, as well as economic and sustainable production. Among cellulose-based structures, cellulose nanofibrils and nanocrystals display nanoscale lateral dimensions and lengths ranging from nanometers to micrometers. Their excellent mechanical properties are, in part, due to their crystalline assembly via hydrogen bonds. Owing to their abundant surface hydroxyl groups, they can be easily modified with nanoparticles, (bio)polymers, inorganics, or nanocarbons to form functional fibers, films, bulk matter, and porous aerogels and foams. Here, some of the recent progress in the development of advanced materials within this rapidly growing field is reviewed.

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Advanced Materials through Assembly of Nanocelluloses.

Nanocellulose is a renewable and biocompatible nanomaterial with a high strength low density and tunable surface chemistry This review summarizes the main processing routes and significant properties of nanocellulose-based foams and aerogels Challenges, such as how to produce long-term stable wet foams or how to avoid structural collapse of the material during solvent removal using eg supercritical drying, are discussed Recent advances in the use of ice templating to generate iso- or anisotropic foams with tunable mechanical and thermal properties are highlighted We illustrate how the porous architecture and properties of nanocellulose-based foams and aerogels can be tailored for applications in eg thermal insulation and energy storage

/pdf/nanocellulose-based-foams-and-aerogels-processing-properties-57a7ubr1er.pdf

Nanocellulose-based foams and aerogels: processing, properties, and applications

A technique is described that measures the instantaneous three-dimensional temperature distribution in water using two-color laser-induced fluorescence (LIF). Two fluorescent dyes, Rhodamine B and Rhodamine 110, are used as temperature indicators. A laser light sheet scanned across the entire measurement volume excites the fluorescent dye, and an optical system involving a color beam splitter gives the intensity distribution of the individual fluorescent dyes on two separate monochrome CCD cameras. The ratio of these fluorescence intensities at each point of the image is calibrated against the temperature to eliminate the effect of the fluctuation of illuminating light intensity. A stable thermally stratified layer was measured by this system to evaluate the total accuracy of the measurement system. The random error of the measurement was ±1.4 K with 95% confidence. Measurements of thermal convection over a heated horizontal surface show temperature iso-surfaces having typical structures such as plumes, ridges and thermals.

Whole Field Measurement of Temperature in Water Using Two-Color Laser Induced Fluorescence

A tremendous amount of wheat straw (WS) has been generated by wheat crops every year, while only a small percentage is being used in applications, and most get burned on the field, causing a large amount of the exhaust gas that pollutes the environment. Herein, we report on the extraction of cellulose nanofibrils (CNF) from the alkali treated WS by a combination of TEMPO-oxidation and mechanical disintegration method. The crystalline structures, thermal properties, natural charge of the CNF were examined. The resultant nano-building blocks of CNF was assembled into macroscopic cellulose materials, i.e., film, aerogel, and filament in this work. Furthermore, the morphologies and microstructues as well as other properties of these three kinds of the CNF assemblies were investigated. The obtained CNF and its assemblies showed a potential application in new materials areas. This work explored a new way to utilize the discarded WS instead of being burned.

Utilization of discarded crop straw to produce cellulose nanofibrils and their assemblies

A combination of extensional rheological and in situ synchrotron radiation small-angle X-ray scattering (SR-SAXS) measurements was introduced to investigate critical strain e* for shish formation and validate whether coil−stretch transition or stretched-network is responsible for shish-kebab formation in high density polyethylene melt. With strain rates e larger than a specific value, the critical strain e* required to induce shish formation turns out to be a constant of about 1.57, which ensure full extension of chain segments with critical entanglement molecular weight locked between two adjacent entanglement points. The results clearly demonstrate that the formation of shish-kebab in polymer melt stems from stretched network instead of coil−stretch transition.

Critical Strain for Shish-Kebab Formation

Cellulose nanofibrils (CNF), as a kind of renewable, sustainable and biodegradable natural-based nanomaterial, have shown great potential application in numerous fields due to their fascinating properties. Some properties of CNF-based materials are closely related to their cellulose polymorph and crystallinity index. In this work, we present a facile method for the generation of CNF with tunable polymorphs and crystallinity via the alkali treatment of jute fibers under various conditions followed by (TEMPO)-mediated oxidation and mechanical disintegration. The changes of the cellulose polymorphs and crystallinity induced by alkali treatment on the jute fibers and consequently obtained CNF were well investigated by synchrotron radiation wide-angle X-ray scattering (SR-WAXS), Fourier transform infrared spectra (FTIR) and differential scanning calorimetry (DSC), respectively. Moreover, the morphology of the as-prepared CNF was also examined by transmission electron microscopy (TEM). It has been found that the CNF showed an identical cellulose polymorph to their source material, but a much higher crystallinity index, which revealed the feasibility of CNF generated from jute fibers with tunable polymorphs and crystallinity indexes.

Fenggang Bian

Papers

Utilization of discarded crop straw to produce cellulose nanofibrils and their assemblies

Critical Strain for Shish-Kebab Formation

Cellulose nanofibrils generated from jute fibers with tunable polymorphs and crystallinity

Cellulose nanofibrils aerogels generated from jute fibers.

Cellulose nanofibrils extracted from the byproduct of cotton plant