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1.
ACS Appl Mater Interfaces ; 11(24): 21865-21873, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31185563

RESUMO

Development and fabrication of novel proton exchange membranes (PEMs) with excellent performance have a great significance to the commercial application of PEM fuel cell. Inspired from the proton-conducting mechanism, γ-poly(glutamic acid) (γ-PGA) nanofibers (NFs) are first fabricated by solution blowing with the help of polylactic acid (PLA) and designed to form amino acid arrays as efficient proton channels for PEMs. The NFs with 50% γ-PGA exhibit a high proton conductivity of 0.572 S cm-1 at 80 °C/50% relative humidity (RH), and 1.28 S cm-1 at 40 °C/90% RH. Density functional theory is carried out to explain the mechanisms of proton hopping in γ-PGA, and the activation energy barriers from NH to COO- for trans and cis conformations under anhydrous conditions are only 0.64 and 0.62 eV, respectively. Then the γ-PGA/PLA NFs are incorporated into sulfonated poly(ether sulfone) to prepare PEMs, which show remarkable performance compared with the Nafion membrane. The composite membrane with 30 wt % NFs exhibits the highest proton conductivity (0.261 S cm-1 at 80 °C/100% RH). The direct methanol fuel cells with this membrane show a maximum power density (202.3 mW cm-2) among all of the PEMs, showing great application potential in the field of PEMs.

2.
Nat Commun ; 10(1): 842, 2019 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-30783091

RESUMO

Proton exchange membranes with short-pathway through-plane orientated proton conductivity are highly desirable for use in proton exchange membrane fuel cells. Magnetic field is utilized to create oriented structure in proton exchange membranes. Previously, this has only been carried out by proton nonconductive metal oxide-based fillers. Here, under a strong magnetic field, a proton-conducting paramagnetic complex based on ferrocyanide-coordinated polymer and phosphotungstic acid is used to prepare composite membranes with highly conductive through-plane-aligned proton channels. Gratifyingly, this strategy simultaneously overcomes the high water-solubility of phosphotungstic acid in composite membranes, thereby preventing its leaching and the subsequent loss of membrane conductivity. The ferrocyanide groups in the coordinated polymer, via redox cycle, can continuously consume free radicals, thus helping to improve the long-term in situ membrane durability. The composite membranes exhibit outstanding proton conductivity, fuel cell performance and durability, compared with other types of hydrocarbon membranes and industry standard Nafion® 212.

3.
Soft Matter ; 14(44): 8879-8882, 2018 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-30378629

RESUMO

A novel hierarchical nanofibrous membrane was demonstrated via in situ self-assembly of 1,3:2,4-dibenzylidene-d-sorbitol (DBS) supramolecular fibrils in solution-blown polyacrylonitrile (PAN) nanofibers. The formed DBS fibrils were interconnected into networks and anchored onto the PAN nanofibers, which decreased the pore sizes and enhanced the mechanical properties, the filtration efficiency, and particularly the flux.

4.
Carbohydr Polym ; 184: 299-306, 2018 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-29352922

RESUMO

Cellulose nanofibers were embedded into sulfonated poly (ether sulfone) matrix to heighten the water retention and proton conductivity of proton exchange membranes (PEMs). Cellulose nanofibers were obtained by hydrolyzing cellulose acetate nanofibers, which were prepared via electrostatic-induction-assisted solution blow spinning. Morphology, thermal stability, and mechanical properties of the PEMs were investigated. The results showed that proton conductivity, water uptake, and methanol permeability of the composite membranes were improved. Hydrophilicity of the composite membranes was gradually improved with the addition of nanofibers. When the content of nanofibers was 5 wt%, the highest proton conductivity was 0.13 S/cm (80 °C, 100% RH). Therefore, the cellulose nanofiber could be used as support materials to enhance the performance of proton exchange membranes, the composite membranes have potential application in Direct methanol fuel cells (DMFCs).

5.
Biomacromolecules ; 19(3): 731-739, 2018 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-29309730

RESUMO

N-Alkylated chitosan (NACS) may improve the blood clotting efficiency of chitosan (CS). To study its blood coagulation capability, a series of NACSs with various carbon chain lengths and degrees of substitution (DS) of alkyl groups were synthesized and characterized by FTIR, NMR, elemental analysis, and X-ray diffraction (XRD). The corresponding NACS nanofiber membranes (NACS-NM) were subsequently fabricated by electronic spinning technique. SEM, XRD, DSC, surface area, porosity, contact angle, blood absorption, and mechanical properties were used to characterize the CS-NM/NACS-NM. Moreover, cytotoxicity, coagulation, activated partial thromboplastin time, plasma prothrombin time, thrombin time, and platelet aggregation tests were performed to evaluate the biocompatibility and blood coagulation properties of NACS-NM. The results showed that NACS-NM was not cytotoxic. NACS-NM with DS of 19.25% for N-hexane CS (CS6b), 17.87% for N-dodecane CS (CS12b), and 8.97% for N-octadecane CS (CS18a) exhibited good blood clotting performance. Moreover, NACS-NMs favored the activation of coagulation factors and platelets. In addition, intracellular Ca2+ was not related to platelet activation. The above results suggested that NACS-NM would be an effective hemostatic agent.


Assuntos
Coagulação Sanguínea , Quitosana/química , Teste de Materiais , Membranas Artificiais , Nanofibras/química , Animais , Testes de Coagulação Sanguínea , Linhagem Celular , Humanos , Coelhos
6.
Carbohydr Polym ; 140: 195-201, 2016 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-26876844

RESUMO

To balance the relationship among proton conductivity and mechanic strength of sulfonated poly(ether sulfone) (SPES) membrane, chitin nanowhisker-supported nanocomposite membranes were prepared by incorporating whiskers into SPES. The as-prepared chitin whiskers were prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) mediated oxidation of α-chitin from crab shells. The structure and properties of the composite membranes were examined as proton exchange membrane (PEM). Results showed that chitin nanowhiskers were dispersed incompactly in the SPES matrix. Thermal stability, mechanical properties, water uptake and proton conductivity of the nanocomposite films were improved from those of the pure SPES film with increasing whisker content, which ascribed to strong interactions between whiskers and between SPES molecules and chitin whiskers via hydrogen bonding. These indicated that composition of filler and matrix got good properties and whisker-supported membranes are promising materials for PEM.


Assuntos
Quitina/química , Fontes de Energia Elétrica , Nanoestruturas/química , Polímeros/química , Prótons , Sulfonas/química , Ácidos Sulfônicos/química , Óxidos N-Cíclicos/química , Fenômenos Mecânicos , Membranas Artificiais , Oxirredução , Temperatura Ambiente , Água/química
7.
Carbohydr Polym ; 101: 1116-21, 2014 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-24299882

RESUMO

Both nanofiber mats and hydrogel have their own advantages in wound healing. In this study, a novel hydrogel nanofiber mats were fabricated via solution blowing of chitosan and PVA solution, with various content of ethylene glycol diglycidyl ether (EGDE) as cross-linker. SEM observation showed that the fibers were several hundred nanometers in diameter with smooth surface and distributed randomly forming three-dimensional mats. The structure of the chitosan/PVA nanofibers was examined by FTIR and XPS, and the results showed that the cross-linking reaction occurred between EGDE and the hydroxyl groups. The mats could quickly hydrate in an aqueous environment to form hydrogel. Their value of equilibrate water absorption varied from 680 to 459% various content of EGDE. The nanofiber mats showed good bactericidal activity against Escherichia coli. The chitosan/PVA hydrogel nanofiber mats showed the combination advantages of nanofibrous mats and hydrogel dressing, and were suggested as potential application in wound healing.


Assuntos
Antibacterianos/química , Quitosana/química , Hidrogéis/química , Nanofibras/química , Nanotecnologia/métodos , Álcool de Polivinil/química , Antibacterianos/farmacologia , Escherichia coli/efeitos dos fármacos , Hidrogéis/farmacologia , Soluções
8.
Carbohydr Polym ; 90(2): 982-7, 2012 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-22840029

RESUMO

Solution blowing is an innovative process for spinning micro-/nano-fibers from polymer solutions using high-velocity gas flow as fiber forming driving force. Submicron-scale cellulose fibers were successfully solution blown by two improvement measures. First, cellulose solution was directly blown to fibers of 260-1900 nm in diameter by raising the air temperature along the spinning line which was proved to accelerate the evaporation of solvent and fiber forming. Second, coaxial solution blowing technique was established with cellulose solution and polyethylene oxide (PEO) solution used as core and shell liquids, respectively. The core-shell structures of the fibers were examined by SEM and TEM. Cellulose fibers with diameter between 160 nm and 960 nm were further obtained after removing PEO shell. X-ray diffraction studies showed that the two kinds of submicron-scale cellulose fibers are mostly amorphous.


Assuntos
Celulose/química , Celulose/ultraestrutura , Nanofibras/ultraestrutura , Indústria Têxtil/métodos , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Modelos Biológicos , Nanofibras/química , Polietilenoglicóis/química , Polietilenoglicóis/farmacologia , Soluções , Temperatura Ambiente , Têxteis/análise
9.
Carbohydr Polym ; 89(1): 104-10, 2012 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-24750610

RESUMO

O-carboxymethyl chitosan sodium salt (NaCMCh), which has good antibacterial activity and solubility in N-methylmorpholine-N-oxide (NMMO) after being treated by sodium hydroxide solution, was blended with cellulose NMMO/H2O solution to study the spinnability. The effect of molecular weight on antibacterial activity and solubility was discussed. The optimal range of molecular weights is from 8 x 104 to 1.9 x 105). The rheological properties of NaCMCh/cellulose polyblends in steady-shear were investigated. The results are presented using appropriate master curves for the temperature and concentration effects. The flow behavior index of the polyblends increase with increasing temperature and NaCMCh content. Apparent viscosity and zero-shear viscosity decrease, but the critical shear rate increases due to the addition of NaCMCh. The polyblends with NaCMCh display a lower structural viscosity index. Finally, the fibers were successfully spun using the lyocell process with NMMO/H2O and the fibers with NaCMCh exhibit good mechanical properties and moisture absorption.


Assuntos
Antibacterianos/química , Celulose/química , Quitosana/análogos & derivados , Óxidos N-Cíclicos/química , Morfolinas/química , Quitosana/química , Quitosana/farmacologia , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Solubilidade , Viscosidade
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