Search

Facile preparation of super tough hydrogels with low temperature tolerance and anti-swelling property is still a challenging task for researchers. Meanwhile, the vast majority of tough hydrogels were obtained though chemical crosslinking and complicated synthesis or processing method accompanying a large number of harmful chemical reagents. Herein, the super tough chitosan/poly(vinyl alcohol) (CS/PVA) hydrogels (the maximum compressive strength of 18.97 MPa at a strain of 80% and the maximum tensile strength of 4.02 MPa at a strain of 406.4%) were successfully prepared via a simple post-treatment method. CS/PVA hydrogels were firstly prepared by freezing-thawing process and then soaking in saturated sodium chloride aqueous solution. The resultant hydrogels possess excellent swelling resistance and low temperature tolerance. This work shows that the post-treatment of immersing in saline solution is a feasible way to prepare super tough hydrogels with low temperature tolerance and anti-swelling property. This also would enlarge the application areas of CS., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A novel magnetic bioadsorbent beads composed of Fe 3 O 4 , chitosan, and Al(OH) 3 (Fe 3 O 4 /CS/Al(OH) 3 ) was synthesized by a modified solvothermal and in-situ reaction. The composite adsorbent was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and vibrating sample magnetometer, respectively. Adsorption toward F - onto Fe 3 O 4 /CS/Al(OH) 3 was investigated as a function of Fe 3 O 4 concentration, initial solution pH, adsorbent dosage, initial fluorion concentration, co-existing ions in water and initial temperature. The addition of Fe 3 O 4 could enhance the adsorption properties of CS/Al(OH) 3 . The saturated adsorption capacity of magnetic Fe 3 O 4 /CS/Al(OH) 3 calculated from the Langmuir isotherm model was 76.63mg/g at 298K. The adsorption isotherm of F - followed Langmuir isotherm model and the adsorption kinetics fitted better to the pseudo-second order kinetic model. The influence of temperature confirmed that the adsorption was spontaneous and endothermic. The magnetic Fe 3 O 4 /CS/Al(OH) 3 beads could be easily separated from water under a low magnetic field., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Integrating high ionic conductivity and robust mechanical properties into one hydrogel remains challenging to date. In this paper, poly(vinyl alcohol)/carboxymethyl chitosan/tannic acid/NaCl/glycerol (PCTNG) organohydrogel was prepared by introducing tannic acid (TA), NaCl and glycerol (Gly) into poly(vinyl alcohol)/carboxymethyl chitosan (PVA/CMCS) simultaneously. Owing to the multiple hydrogen bonding complexations, the salting-out effect and metal coordination, the PCTNG organohydrogel showed an attractive overall performance with high tensile strength (2.02 MPa), large elongation at break (570.82%), superb ionic conductivity (3.05 S/m), excellent thermoplasticity and thermally assisted self-healing ability. Moreover, the introduction of Gly made PCTNG organohydrogel had high anti-freezing and anti-dehydration properties. The introduction of TA and NaCl endowed PCTNG organohydrogel with anti-bacterial properties. A flexible strain sensor was made based on this organoydrogel and this strain sensor could detect various human activities. This study provided a simple and promising strategy for manufacturing ionic conductive organohydrogel for flexible wearable devices. [ABSTRACT FROM AUTHOR]

In this paper, we fabricated a tough, anti-freezing (freezing point of − 25.5 °C) and ionic conductive carboxymethyl chitosan (CMCS)-based double-network (DN) hydrogel by a free radical polymerization and Al3+ coordination. In greater detail, the PAM/CMCS-Al3+ hydrogel was composed of Al3+-coordinated CMCS network and covalently crosslinked PAM network. The hybrid DN structure of PAM/CMCS-Al3+ hydrogel gave rise to high mechanical properties (tensile strength up to 2.15 MPa, elongation at break up to 1741%, toughness of 13.2 MJ/m3 and elastic modulus of 1.43 MPa) and good fatigue resistance. PAM/CMCS-Al3+ hydrogel not only exhibited the capacity to conduct electricity via free ions, but also had good strain sensitivity (GF = 2.09, 0–200% strain and fast response time of 234 ms). Based on the high strain sensitivity, PAM/CMCS-Al3+ hydrogel could be used to assemble a flexible strain sensor with the ability to precisely detect human motions.Kindly check and confirm the edit made in the title.We agree with the edit made in the title. [ABSTRACT FROM AUTHOR]

The AlCl 3 ·6H 2 O aqueous solution was used to dissolve chitosan (CS) and the CS/poly(vinyl alcohol) (PVA) blend films were prepared at the absence of acetic acid. AlCl 3 ·6H 2 O was retained in CS/PVA film and glycerol was added to form the complex plasticizer with AlCl 3 ·6H 2 O. The effect of glycerol on the water sorption, crystalline, thermal and mechanical properties of AlCl 3 ·6H 2 O doped CS/PVA film was studied by atomic force microscopy, X-ray diffraction, thermal gravity analysis and tensile testing, respectively. The experimental results showed that glycerol had a significant positive effect on the properties of AlCl 3 ·6H 2 O doped CS/PVA films. With the synergism effect of AlCl 3 ·6H 2 O and glycerol, the prepared CS/PVA films showed excellent mechanical properties. With the addition of 30 wt% glycerol, the AlCl 3 ·6H 2 O doped CS/PVA films behave the tensile strength of 39 MPa and elongation at break of 120%, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Novel MnO 2 -doped holey carbon materials were obtained by an efficient and facile synthetic method using chitosan, potassium hydroxide and potassium permanganate as the raw materials. The carbon framework with high specific surface area was derived from chitosan by carbonization and activation approach, afterwards, MnO 2 nanorods were grown on the surface of porous carbon by one-step agitation method and the MnO 2 -doped holey carbon material was obtained. The scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, X-ray diffraction, N 2 adsorption-desorption measurements, Raman spectroscopy and X-ray photoelectron spectroscopy were employed to analyze the physicochemical characteristics of the MnO 2 -doped holey carbon materials. The electrochemical performance of these materials displayed well through relative tests including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy measurements in 6.0 M KOH solution. Especially, this as-obtained electrode material with the optimum ratio presented a high gravimetric capacitance (460F g−1 at 0.2 A g−1) and exceptional capacitance reservation (91.67% at 10 A g−1 over 10,000 cycles) in the three-electrode system with 6.0 M KOH solution as the electrolyte. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Porous polyHIPEs were prepared via HIPE template stabilized by a gemini surfactant. • The polyHIPEs possess high porosity and hierarchically porous structures. • The polyHIPE exhibited relatively high adsorption capacity and adsorption rate. Abstract In this work, a gemini-surfactant (i.e. sodium dilauramino cysteine, SDLC) stabilized high internal phase emulsion (HIPE) template was utilized to prepare monolithic polyHIPEs of chitosan- g -polyacrylamide (CT- g -PAAm) for the first time. The influences of internal phase fraction and emulsifier concentration on the porous structures were studied. The morphologies of polyHIPEs were observed via scanning electron microscope (SEM) while structure parameters were investigated by combining nitrogen adsorption/desorption measurements with mercury intrusion porosimetry (MIP). Highly porous polyHIPEs of CT- g -PAAm with porosity varying from 86 to 93% were obtained at different internal phase fractions. PolyHIPEs were also prepared using Tween 20 as the emulsifier for comparison. It was found the polyHIPE using SDLC emulsifier (S-polyHIPE) showed higher porosity and consequent smaller foam density than that using Tween 20 emulsifier (T-polyHIPE), implying the gemini-surfactant can act as a novel type of promising emulsifier for the preparation of porous polyHIPEs. In addition, the adsorption performances of polyHIPEs were evaluated by adsorbing methylene blue (MB). At the same internal phase fraction, S-polyHIPE showed higher adsorption capacity and faster adsorption rate than T-polyHIPE. The adsorption data were analyzed by isotherm models and dynamic models, respectively. The results indicated that the adsorption occurs as a monolayer on the adsorbent surface with equal adsorption sites. [ABSTRACT FROM AUTHOR]

Nitrogen and boron co-doped activated carbon (BKACS) was synthesized through the carbonization, KOH activation and subsequently hydrothermal doping reaction process with chitosan as the renewable carbon source. The prepared samples were characterized by XRD, SEM, Raman, XPS and BET for their structure, morphology, specific surface area and elemental composition, respectively. The obtained BKACS has a specific surface area of 1129.6 m 2  g −1 , with high conductivity and capacitive character. The BKACS was applied as the electrode material to fabricate the electrochemical double-layer supercapacitor. The supercapacitor performed a high specific capacitance of 316 F g −1 at 0.2 A g −1 in a three-electrode system in the 6 M KOH electrolyte and excellent cycling stability with a capacitance retention of 94.08% after 10,000 cycles at 10 A g −1 . The attractive supercapacitor performance of the BKACS material has the high power density, excellent cycling life, and environmental friendliness, making it potentially a promising replaceable function for future energy storing device. [ABSTRACT FROM AUTHOR]

In this study, a series of novel quaternized poly(vinyl alcohol)/chitosan/molybdenum disulfide (QPVA/CS/MoS 2 ) anion exchange membranes (AEMs) were prepared for direct methanol alkaline fuel cell (DMAFC). The composite membrane was synthesized by adding different amounts of MoS 2 nanosheets (0, 0.1, 0.2, 0.5 and 1 wt%) into QPVA/CS mixture solution and using the solution casting method. The crystallinity, thermal and mechanical properties, ion conductivity and resistance to methanol of the QPVA/CS/MoS 2 membranes were characterized by X-ray diffraction, thermogravimetric analysis, tensile testing, ion exchange capacity, and methanol permeability measurements, respectively. The MoS 2 was homogeneously dispersed in the membranes. The mechanical strength of the composite membranes was enhanced with the addition of MoS 2 . With the addition of 1.0 wt% MoS 2 , the QPVA/CS/MoS 2 composite membrane has the lowest methanol permeability of 0.210 × 10 −7 cm 2 ·s −1 . This study confirmed that the novel QPVA/CS/MoS 2 membrane would be a potential candidate for the application in DMAFCs. [ABSTRACT FROM AUTHOR]

Development of bio-based hydrogels with good mechanical properties is of great importance for their excellent biocompatibility and biodegradability. In this paper, chitosan (CS) based double network (DN) hydrogel was prepared by dissolving CS in AlCl 3 ·6H 2 O aqueous solution instead of acetic acid solution. After dissolving acrylic amide (AM), acrylic acid (AA), N, N’-methylenebisacrylamide and 2-hydroxy-4′-(2-hydoxyethoxy)-2-methylpropiophenone were added into the CS/Al 3+ solution and the CS/PAMAA-Al 3+ DN hydrogel was prepared by UV polymerization. The hybrid physical and chemical crosslinked network hydrogels were prepared. The tensile and compression properties of CS/PAMAA-Al 3+ DN hydrogel were studied. The results showed that the CS/PAMAA-Al 3+ DN hydrogels have high toughness, stretch-ability, and excellent shape recovery properties. The CS/PAMAA-Al 3+ DN hydrogel could show the tensile strength of 0.54 MPa and elongation at break of 2203.7%. These properties arise from the dynamic ionic interaction between Al 3+ and CS/PAMAA macromolecular chains. [ABSTRACT FROM AUTHOR]

Carbon materials with hierarchical porous structure and heteroatom-doping have gained extensive attention as promising electrode for supercapacitors. In this study, we report a facile approach which involves only one step of calcination and washing treatment to prepare nitrogen-doped carbon material with tunable pore structure. This carbon material was derived from chitosan employing the blend of potassium nitrate and hexahydrate magnesium nitrate as the active agent. By adjusting the calcination temperature and active agents, the morphology and pore structure of the material can be effectively controlled. By means of this approach, the three-dimensional hierarchical porous carbon possesses a large specific surface area of 922 m2 g−1, and abundant nitrogen and oxygen functional groups. Benefiting from these advantages, the final product shows high specific capacitance of 225.3 F g−1 in a three-electrode system at 1 A g−1, good cycle stability with 88% capacity retention after 10000 cycles at 5 A g−1. Additionally, the constructed symmetric two-electrode supercapacitor shows remarkable specific energy of 10.46 Wh kg−1 with the specific power of 500.08 W kg−1. It also showed excellent electrochemical performance in PVA/KOH hydrogel electrolyte with 70.8 F g−1 at the current density of 1 A g−1. [Display omitted] • This hierarchical porous carbon material was prepared from chitosan through one-step high-temperature carbonization. • The blend of potassium nitrate and magnesium nitrate was employed as the active agent. • The pore size of HPCMgK-600 mainly distributed in micro and mesopores at around 0.5 and 3.5 nm. • HPCMgK-600 displayed high performance as the electrode for supercapacitor. [ABSTRACT FROM AUTHOR]