Conducting polymer hydrogels (CPHs) have emerged as a fascinating class of smart soft matters important for various advanced applications. However, achieving the synergistic characteristics of cond...

Nanocellulose-Mediated Electroconductive Self-Healing Hydrogels with High Strength, Plasticity, Viscoelasticity, Stretchability, and Biocompatibility toward Multifunctional Applications.

How to rationally design the microstructure of polymer nanocomposites to significantly improve their electromagnetic interference shielding effectiveness (EMI SE) is still a great challenge. Herein, we developed a template method for fabricating 3D porous graphene nanoplatelets/reduced graphene oxide foam/epoxy (GNPs/rGO/EP) nanocomposites, in which 3D rGO foam embedded with GNPs constructs a 3D electrical and thermal conductive network in the EP matrix. The 3D rGO framework resolves the agglomeration problem of GNPs, acts as an efficient bunch of channels for electrical transport and attenuates the entered electromagnetic wave. Benefiting from this 3D nanohybrid framework, the GNPs/rGO/EP nanocomposites containing 0.1 wt% rGO and 20.4 wt% GNPs exhibit an EMI SE value of 51 dB in the X-band range, an almost 292% improvement relative to the rGO/EP nanocomposites (∼13 dB) and 240% enhancement compared with the GNPs/EP nanocomposites without 3D microstructures (∼15 dB) and an excellent thermal conductivity of 1.56 W mK−1 and electrical conductivity up to 179.2 S m−1. This work provides a new strategy for the design of muti-functional epoxy nanocomposites for EMI shielding and efficient heat dissipation.

Superior electromagnetic interference shielding 3D graphene nanoplatelets/reduced graphene oxide foam/epoxy nanocomposites with high thermal conductivity

Cellulose, a well-known fascinating biopolymer, has been considered to be a sustainable feedstock of energy sources and chemical engineering in the future. However, due to its highly ordered structure and strong hydrogen bonding network, cellulose is neither meltable nor soluble in conventional solvents, which limits the extent of its application. Therefore, the search for powerful and eco-friendly solvents for cellulose processing has been a key issue in this field for decades. More recently, certain ionic liquids (ILs) have been found to be able to efficiently dissolve cellulose, providing a new and versatile platform for cellulose processing and functionalization. A series of cellulose-based materials, such as films, fibers, gels and composites, have been produced readily with the aid of ILs. This review article highlights recent advances in the field of dissolution and processing of cellulose with ILs. It is hoped that this review work will stimulate a wide range of research studies and collaborations, leading to significant progress in this area.

Application of ionic liquids for dissolving cellulose and fabricating cellulose-based materials: state of the art and future trends

This study investigated the impact of cellulose polymorphs on cellulose nanocrystals (CNCs) preparation. Cellulose samples with different types of polymorphs (cellulose I, cellulose II, and cellulose III) were prepared. Subsequently, CNCs were obtained from the above cellulose samples by sulfuric acid hydrolysis. The initial cellulose and CNCs were characterized by X-ray diffraction (XRD), thermo gravimetric analysis (TGA), scanning electronic microscopy (SEM) and particle size distribution (PSD). A comparative study showed that the properties of CNCs were closely related to the polymorphs of initial cellulose. The original polymorphs of cellulose I and cellulose II were retained, while that of cellulose III was converted back to cellulose I during the sulfuric acid hydrolysis process of CNCs preparation. For cellulose I and cellulose II, the crystallinity of both corresponding CNCs continuously increased with the increase of sulfuric acid concentration, until reaching a maximum at approximately 84.0%, while the crystallinity of CNCs obtained from cellulose III was slightly affected by sulfuric acid concentration. The yields of CNCs obtained from cellulose II and cellulose III with 61 wt% H2SO4 were extremely high, reaching 46.8% and 43.4%, respectively. Smaller CNCs particles with short-length were obtained by sulfuric acid hydrolysis of cellulose II. In addition, the properties (yield, dimension and thermal degradation behavior) of CNCs obtained from cellulose III were more susceptible to the acid concentration compared with those of CNCs obtained from cellulose I.

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Research on cellulose nanocrystals produced from cellulose sources with various polymorphs

With the extensive use of portable and wearable electronic devices, ultrathin electromagnetic interference (EMI) shielding materials with excellent thermal management are increasingly desirable. In this study, ultrathin and highly aligned reduced graphene oxide (RGO)/cellulose nanofiber (CNF) composite films with excellent EMI shielding performance and strong anisotropy of thermal conductivity were fabricated by vacuum-assisted filtration followed by hydroiodic acid (HI) reduction. The obtained 50 wt% RGO/CNF composite films, which are only ≈23 μm in thickness, possess the remarkable electrical conductivity of ≈4057.3 S m−1 and outstanding EMI shielding effectiveness (SE) of ≈26.2 dB owning to the uniform dispersion and self-alignment into the layered structure of RGO. In addition, the RGO/CNF composite films with 50 wt% RGO loadings possess high in-plane thermal conductivity (K ≈ 7.3 W m−1 K−1) and, unexpectedly, very low cross-plane thermal conductivity (K⊥ ≈ 0.13 W m−1 K−1), resulting in strong anisotropy of the thermal conductivity (K/K⊥ ≈ 56). Thus, these ultrathin RGO/CNF composite films have great application potential as effective lightweight shielding materials against electromagnetic microwaves and heat, especially in flexible portable electronic devices and wearable devices.

Ultrathin flexible reduced graphene oxide/cellulose nanofiber composite films with strongly anisotropic thermal conductivity and efficient electromagnetic interference shielding

Cellulose acetate fibers prepared from different raw materials with rapid synthesis method

In this study, graphite powder (GP) was introduced into the conductive cellulose/polypyrrole (PPy) composite films to increase their conductivity and thermal stability. The GP was dispersed in ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) before the dissolution of cellulose, and the cellulose/GP/PPy films were prepared by in situ chemical polymerization of PPy nanoparticles on the film surface. The structural characteristics and properties of the composite films were investigated in detail. The GP flakes, which were embedded in the cellulose matrix, increased the thickness and decreased the density of the films, leading to the decrement of mechanical properties. However, the thermal stability of the films was significantly improved by the incorporation of graphite, and the composite film could even substantially maintain the original shape after being burned. In addition, the electrical conductivity of the films was increased seven times, leading to the excellent electromagnetic interference shielding effectiveness. The cellulose/GP/PPy film could be considered as a potential candidate for the effective lightweight electromagnetic interference shielding materials in electronics, radar evasion, aerospace, and other applications.

Highly thermostable, flexible, and conductive films prepared from cellulose, graphite, and polypyrrole nanoparticles.

Effects of polymorphs on dissolution of cellulose in NaOH/urea aqueous solution

In this study, the effect of alkaline pretreatment on preparation of regenerated lignocellulose fibers from bamboo stem was studied in detail. Prior to being dissolved in [Emim]OAc, bamboo stems were ground and treated with different concentrations of sodium hydroxide solutions. The obtained spinning dopes were then extruded into water coagulation bath and regenerated to composite fibers. The properties of the raw materials, spinning dopes, and regenerated fibers were investigated. Results showed that alkaline pretreatment could break the rigid structure of lignocelluloses by removing part of hemicelluloses and lignin as well as changing the polymorphous lattice and C
 r
 I of cellulose. The increased specific surface area of raw materials enhanced the accessibility of solvent, promoted the swelling process and shortened the dissolution time. The viscosity of the spinning dopes and the strength of the regenerated fiber reached the maximum value when the bamboo powder was treated with 20 wt% sodium hydroxide at 60 °C for 4 h. In addition, the fibers prepared from the alkali-treated raw materials showed round cross-section and wrinkled surface. Therefore, the properties of the regenerated lignocellulose fibers could be improved by employing an appropriate alkali pretreatment of raw materials.

Effect of alkaline pretreatment on the preparation of regenerated lignocellulose fibers from bamboo stem

Hemicelluloses-based hydrogel coated with Ag nanoparticles was prepared by reduction of Ag ions in cross-linked dialdehyde hemicelluloses (DHC)/chitosan hydrogels, and the hydrogel network was fabricated from two kinds of macromolecules from biobased materials. This is an effective and environmental approach, which is developed to introduce an antimicrobial property into the hydrogel network without any reductants. The hydrogel was formed through the Schiff base reaction between the amino groups of chitosan chains and the aldehyde groups of DHC. The swelling property of the hydrogel decreased from 1129 to 54.8 g/g after the addition of silver ions. Importantly, the DHC/chitosan/Ag hydrogel possessed antimicrobial activity against the model microbes Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive), which is a promising antimicrobial material for applications in the biomedical field.

Jinghuan Chen

Papers

Cellulose acetate fibers prepared from different raw materials with rapid synthesis method

Highly thermostable, flexible, and conductive films prepared from cellulose, graphite, and polypyrrole nanoparticles.

Effects of polymorphs on dissolution of cellulose in NaOH/urea aqueous solution

Effect of alkaline pretreatment on the preparation of regenerated lignocellulose fibers from bamboo stem

Fabrication of Biopolymer Hydrogel Containing Ag Nanoparticles for Antibacterial Property