Optically Transparent and Toughened Poly(methyl methacrylate) Composite Films with Acylated Cellulose Nanofibers

In this work, nanocomposites of poly(methyl methacrylate) (PMMA) with cellulose nanofiber (CNF) were prepared by a solution casting technique. CNF was modified by propionic anhydride (PA) to form surface-propionylated CNF (CNFp) to improve its compatibility with the PMMA matrix. CNF, CNFp, and acetylated CNF were compared with respect to their influence as fillers in PMMA composite films by ultraviolet-visible transmittance, haze values, tensile strength testing, and water contact angle measurement. It was demonstrated that 1 wt % of CNFp has good compatibility and uniform dispersion in the PMMA matrix, as demonstrated by the formation of a smooth surface composite film with good transparency, enhanced tensile properties, improved toughness, and lower wettability. Therefore, PMMA/CNFp composite films have great potential for use in several applications such as lightweight transparent materials, window substitutes, and see-through packaging.

Integration of covalent organic frameworks into hydrophilic membrane with hierarchical porous structure for fast adsorption of metal ions

Covalent organic frameworks (COFs) including their preparation and application as research focus have attracted attention of researchers. Most of COFs exhibit the powder form, therefore they inevitably suffer many difficulties during use of catalysis, separation and so on. In previous study, our group have fabricated COF-based monoliths through ring-opening polymerization in which the micropores/mesopores of COF were easily blocked by unreacted monomer and solvent resulting in low specific surface area of COF-based monoliths. Herein, we designed and fabricated two kinds of hydrazone-linked COF-integrated chitosan membranes (CM@COF and COF@CM) with hierarchical porous structure using chitosan, poly(ethylene glycol) diglycidyl ether (PEGDE), 1,3,5-triformylphloroglucinol (TP), oxalyldihydrazide (ODH) in the presence of mesitylene and 1,4-dioxane, and acetic acid as catalyst. The resulting CM@COF is monolithic material to overcome disadvantages of COF powder, meanwhile it possessed hierarchical porous structure containing mesoporous and macroporous structure and higher specific surface area (117.4 m² g^-1) than chitosan membrane (0.4 m² g^-1). And the CM@COF was applied to adsorption of heavy metal ion, and its adsorption capacities for Cu(II) and Cr(VI) ions were 144 mg g^-1 (pH = 7) and 388 mg g^-1 (pH = 6), respectively, indicating that the CM@COF had potential for fast removal of heavy metal ions.

Fused sphere carbon monoliths with honeycomb-like porosity from cellulose nanofibers for oil and water separation

Carbon monoliths with a unique hierarchical surface structure from carbonized cellulose nanofibers were synthesized in pursuit of developing carbon materials from sustainable natural resources. Through a 2-step hydrothermal - carbonization method, TEMPO-oxidized cellulose nanofibers were turned into carbon-rich hydrochar embedded with polystyrene latex as template for 80 nm-sized pores in a honeycomb pattern, while the triblock copolymer Pluronic F-127 was used for a dual purpose not reported before: (1) an interface between the cellulose nanofibers and polystyrene particles, as well as (2) act as a secondary template as ∼1 μm micelles that form hollow carbon spheres. The use of nanofibers allowed more contact between the carbon spheres to coalesce into a working monolith while optimizing the pore structure. Oil-water separation studies have shown that carbon monoliths have high adsorption capacity due to surface area and hydrophobicity. Testing against commercially available activated carbon pellets show greater performance due to highly-developed macropores.

Fe-Doping induced divergent growth of Ni–Fe alloy nanoparticles for enhancing the electrocatalytic oxygen reduction

Separate (111)- and (200)-faceted Ni–Fe nanoparticles were synthesized and their oxygen reduction reaction activity studied via density functional theory calculations and experiments.

Size-Controlled Preparation of Gold Nanoparticles Deposited on Surface-Fibrillated Cellulose Obtained by Citric Acid Modification

Cellulose-based functional materials have gained immense interest due to their low density, hydrophilicity, chirality, and degradability. So far, a facile and scalable preparation of fibrillated cellulose by treating the hydroxy groups of cellulose with citric acid (F-CAC) has been developed and applied as a reinforcing filler for polypropylene composite. Herein, a size-selective preparation of Au nanoparticles (NPs) stabilized by F-CAC is described. By modifying the conditions of transdeposition method, established in our group previously, a transfer of Au NPs from poly(N-vinyl-2-pyrrolidone) (PVP) to F-CAC proceeded up to 96% transfer efficiency with retaining its cluster sizes in EtOH. Meanwhile, the deposition efficiency drastically decreased in the case of nonmodified cellulose, showing the significance of citric acid modification. A shift of binding energy at Au 4f core level X-ray photoelectron spectroscopy from 82.0 to 83.3 eV indicated that the NPs were stabilized on an F-CAC surface rather than by PVP matrix. The reproducible particle size growth was observed when 2-propanol was used as a solvent instead of EtOH, expanding the range of the available particle size with simple manipulation. The thus-obtained Au:F-CAC nanocatalysts exhibited a catalytic activity toward an aerobic oxidation of 1-indonol in toluene to yield 1-indanone quantitatively and were recyclable at least six times, illustrating high tolerance against organic solvents.

Flexible Solid-State Supercapacitors Derived from Biomass Konjac/Polyacrylonitrile-Based Nitrogen-Doped Porous Carbon

Energy shortage and wasting of resources are two main challenges for human society. To solve these problems, nitrogen-doped porous carbon was synthesized through a simple thermally induced phase separation (TIPS) method with subsequent carbonization and activation with biomass konjac/polyacrylonitrile composites as the raw materials and nitrogen source for the first time. The obtained composite carbon with hierarchical porosity, large specific surface areas, and high content of nitrogen doping shows promise due to its desirable electrochemical performance. Nitrogen-doped porous carbon exhibits a high specific capacitance of 390 F g^-1 in a three-electrode system and a good rate characteristic with 70% capacitance retention at 20 A g^-1. Excellent stabilization was observed with only a 4.5% capacitance decay under 10 000 cycles at 5 A g^-1. The practical application of the composite porous carbon on flexible symmetrical supercapacitors was evaluated, showing a maximum energy density of 9.0 W h kg^-1 when the power density was 250.2 W kg^-1. More importantly, the fabricated flexible supercapacitor could still keep an excellent supercapacitor performance under bending and shows only a slight capacitance loss of 9% even after 1000 cycles (180°) of repetitive bending. The current study promotes the development of nitrogen-doped carbon materials on flexible energy storage devices.

Superfast flow reactor derived from the used cigarette filter for the degradation of pollutants in water

Developing high value-added products from the waste materials is highly promising from the perspective of environmental protection and resource recovery. Herein, the used cigarette filter was recycled to prepare the flow reactor via a clean and facile strategy. A continuous-flow reduction method was adopted to produce the gold nanoparticles on deacetylated cigarette filter without any extra chemical modifier, reductant or surfactant. The obtained filter was applied as a continuous-flow reactor and showed a high permeability and ultrafast flow catalytic ability. The permeability coefficient of the reactor was about 1.4 × 10^-10 m². This work provided a clean method to covert the waste cigarette filter to useful flow reactor with the relatively simple steps, and the product had a potential for the fast reduction of 4-nitrophenol and dyes including methyl blue and methylene orange.

Palladium nanoparticle loaded β-cyclodextrin monolith as a flow reactor for concentration enrichment and conversion of pollutants based on molecular recognition

This study reports pollutant remediation by a catalyst-loaded, β-cyclodextrin cross-linked polymer monolith. The monolith enabled removal of the pollutant to a residual concentration with no environmental effect and conversion of the adsorbed pollutant into useful compounds with enriched concentration, allowing for the adsorption capacity regeneration.

Supramolecular Biocomposite Hydrogels Formed by Cellulose and Host-Guest Polymers Assisted by Calcium Ion Complexes

Hydrogels are biocompatible polymer networks; however, they have the disadvantage of having poor mechanical properties. Herein, the mechanical properties of host-guest hydrogels were increased by adding a filler and incorporating other noncovalent interactions. Cellulose was added as a filler to the hydrogels to afford a composite. Citric acid-modified cellulose (CAC) with many carboxyl groups was used instead of conventional cellulose. The preparation began with mixing an acrylamide-based αCD host polymer (p-αCD) and a dodecanoic acid guest polymer (p-AADA) to form supramolecular hydrogels (p-αCD/p-AADA). However, when CAC was directly added to p-αCD/p-AADA to form biocomposite hydrogels (p-αCD/p-AADA/CAC), it showed weaker mechanical properties than p-αCD/p-AADA itself. This was caused by the strong intramolecular hydrogen bonding (H-bonding) within the CAC, which prevented the CAC reinforcing p-αCD/p-AADA in p-αCD/p-AADA/CAC. Then, calcium chloride solution (CaCl₂) was used to form calcium ion (Ca²⁺) complexes between the CAC and p-αCD/p-AADA. This approach successfully created supramolecular biocomposite hydrogels assisted by Ca²⁺ complexes (p-αCD/p-AADA/CAC/Ca²⁺) with improved mechanical properties relative to p-αCD/p-AADA hydrogels; the toughness was increased 6-fold, from 1 to 6 MJ/m³. The mechanical properties were improved because of the disruption of the intramolecular H-bonding within the CAC by Ca²⁺ and subsequent complex formation between the carboxyl groups of CAC and p-AADA. This mechanism is a new approach for improving the mechanical properties of hydrogels that can be broadly applied as biomaterials.

Orthodontic Aligner Incorporating Eucommia ulmoides Exerts Low Continuous Force: In Vitro Study

The aim of this study was to investigate the orthodontic force exerted by thermoplastic orthodontic appliances incorporating Eucommiaulmoides in terms of usefulness as the aligner-type orthodontic device. Erkodur, Essix C+^®, Eucommia elastomer, and edgewise brackets were used (n = 3, each; thickness = 1.0 mm, each). The orthodontic force on the upper right incisor was measured every 24 h for two weeks using a custom-made measuring device. The force of the Eucommia elastomer (4.25 ± 0.274 N) and multi bracket system (5.32 ± 0.338 N) did not change from the beginning to the end (p > 0.01). The orthodontic force exerted by the Eucommia elastomer was lower than that of the multi-bracket orthodontic appliance from the beginning to the end. The force of Erkodur significantly decreased from the beginning to 24 h (6.47 ± 1.40 N) and 48 h (3.30 ± 0.536 N) (p < 0.01). The force of Essix C+^® significantly decreased from the beginning (13.2 ± 0.845 N) to 24 h (8.77 ± 0.231 N) (p < 0.01). The thermoplastic orthodontic appliance made of Eucommia elastomer continuously exerted a constant orthodontic force for two weeks under water immersion conditions. The orthodontic force of Eucommia elastomer was found to be similar to the orthodontic force exerted by the multi-bracket orthodontic appliance with 0.019 × 0.025 in nickel–titanium wire. These results suggest that the Eucommia elastomer has possibly become one of the more useful materials to form thermoplastic orthodontic appliance exerting low continues orthodontic force.

Controlled preparation of interconnected 3D hierarchical porous carbons from bacterial cellulose-based composite monoliths for supercapacitors

The controlled design and synthesis of porous carbons with anticipated microstructures and morphologies, and a high specific surface area (SSA) have been focused on for supercapacitor development. Here, hierarchical porous carbons (HPCs) with an interconnected three-dimensional morphology derived from a natural-based bacterial cellulose (BC) composite have been successfully prepared by thermally induced phase separation of poly(ethylene-co-vinyl alcohol) (EVOH) and subsequent carbonization/activation. The SSA and porous architectures can be controlled by fine-tuning the preparation conditions such as the precursor morphology and structure, activator dosage and activation temperature, and the relationships between the super-capacitive properties and the SSA and pore size distribution have been further investigated. The obtained porous carbon material possesses a hierarchical porous structure with moderate micropores, favorable mesopores, interconnected macropores, a high SSA of 2161 m² g^-1 and a maximum oxygen-dopant content of 9.99%, enabling an increase in the active materials utilization efficiency and wettability. Due to the synergistic effects of these features, the obtained porous carbon electrode used in a supercapacitor shows a high specific capacitance of 420 F g^-1 at 0.5 A g^-1, excellent rate performance with 75% capacitance retention at 20 A g^-1, and good cycling stability with ∼96.1% retention even after 10 000 continuous charge-discharge cycles at 5 A g^-1. Additionally, the assembled supercapacitor based on porous carbon displays a moderate energy density of 20 W h kg^-1. The good electrochemical performance and facile effective synthesis of bio-derived carbon materials with tunable porous structures indicate promising applications in supercapacitors.

Properties enhancement of carboxymethyl cellulose with thermo-responsive polymer as solid polymer electrolyte for zinc ion battery

A novel polymer host from carboxymethyl cellulose (CMC)/poly(N-isopropylacrylamide) (PNiPAM) was developed for a high safety solid polymer electrolyte (SPE) in a zinc ion battery. Effects of the PNiPAM loading level in the range of 0-40% by weight ( wt%) on the chemical, mechanical, thermal, and morphological properties of the CMC/PNiPAMx films (where x is the wt% of PNiPAM) were symmetrically investigated. The obtained CMC/PNiPAMx films showed a high compatibility between the polymers. The CMC/PNiPAM20 blend showed the greatest tensile strength and modulus at 37.9 MPa and 2.1 GPa, respectively. Moreover, the thermal degradation of CMC was retarded by the addition of PNiPAM. Scanning electron microscopy images of CMC/PNiPAM20 revealed a porous structure that likely supported Zn2+ movement in the SPEs containing zinc triflate, resulting in the high Zn2+ ion transference number (0.56) and ionic conductivity (1.68 × 10-4 S cm-1). Interestingly, the presence of PNiPAM in the CMC/PNiPAMx blends showed a greater stability during charge-discharge cyclic tests, indicating the ability of PNiPAM to suppress dendrite formation from causing a short circuit. The developed CMC/PNiPAM20 based SPE is a promising material for high ionic conductivity and stability in a Zn ion battery.