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In this paper, we successfully synthesize phosphoric acid functionalized graphene oxide (PGO) based on acid modification of graphene oxide. The composite membrane is further prepared by adding PGO into sulfonated poly(aryl ether ketone sulfone) containing carboxyl groups matrix (C-SPAEKS). The PGO as well as the composite membranes were characterized by a series of tests. The prepared composite proton exchange membranes (PEMs) have good mechanical and electrochemical properties. Compared to the C-SPAEKS membrane, the best composite membrane has a tensile strength of 40.7 MPa while exhibiting superior proton conductivity (110.17 mS cm-1 at 80 °C). In addition, the open-circuit voltage and power density of C-SPAEKS@1% PGO are 0.918 V and 792.17 mW cm-2, respectively. Compared with C-SPAEKS (0.867 V and 166 mW cm-2), it can be seen that our work has a certain effect on the improvement of the single cell performance. The above results demonstrate that the functionalized graphene oxide has greatly improved the electrochemical performance and even the overall performance of PEMs.
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Developing novel proton exchange membranes (PEMs) with low cost and superior performance to replace Nafion is of great significance. Polyoxometalate-doped sulfonated poly(aryl ether ketone sulfone) (SPAEKS) allows for the amalgamation of the advantages in each constituent, thereby achieving an optimized performance for the hybrid PEMs. Herein, the hybrid membranes by introducing 2MeIm-{Mo132} into SPAEKS are obtained. Excellent hydrophilic properties of 2MeIm-{Mo132} can help more water molecules be retained in the hybrid membrane, providing abundant carriers for proton transport and proton hopping sites to build successive hydrophilic channels, thus lowering the energy barrier, accelerating the proton migration, and significantly fostering the proton conductivity of hybrid membranes. Especially, SP-2MIMo132-5 exhibits an enhanced proton conductivity of 75 mS cm-1 at 80 °C, which is 82.9% higher than pristine SPAEKS membrane. Additionally, this membrane is suitable for application in proton exchange membrane fuel cells, and a maximum power density of 266.2 mW cm-2 can be achieved at 80 °C, which far exceeds that of pristine SPAEKS membrane (54.6 mW cm-2). This work demonstrates that polyoxometalate-based clusters can serve as excellent proton conduction sites, opening up the choice of proton conduction carriers in hybrid membrane design and providing a novel idea to manufacture high-performance PEMs.
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STUDY DESIGN: Basic science study using a hemisection spinal cord injury (SCI) model. OBJECTIVE: We sought to assess the effect of blocking osteopontin (OPN) upregulation on motor function recovery and pain behavior after SCI and to further investigate the possible downstream target of OPN in the injured spinal cord. SUMMARY OF BACKGROUND DATA: OPN is a noncollagenous extracellular matrix protein widely expressed across different tissues. Its expression substantially increases following SCI. A previous study suggested that this protein might contribute to locomotor function recovery after SCI. However, its neuroprotective potential was not fully explored, nor were the underlying mechanisms. MATERIALS AND METHODS: We constructed a SCI mouse model and analyzed the expression of OPN at different time points and the particular cell distribution in the injured spinal cord. Then, we blocked OPN upregulation with lentivirus-delivering siRNA targeting OPN specifically and examined its effect on motor function impairment and neuropathic pain after SCI. The underlying mechanisms were explored in the OPN-knockdown mice model and cultured vascular endothelial cells. RESULTS: The proteome study revealed that OPN was the most dramatically increased protein following SCI. OPN in the spinal cord was significantly increased three weeks after SCI. Suppressing OPN upregulation through siRNA exacerbated motor function impairment and neuropathic pain. In addition, SCI resulted in an increase in vascular endothelial growth factor (VEGF), AKT phosphorylation, and angiogenesis within the spinal cord, all of which were curbed by OPN reduction. Similarly, OPN knockdown suppressed VEGF expression, AKT phosphorylation, cell migration, invasion, and angiogenesis in cultured vascular endothelial cells. CONCLUSION: OPN demonstrates a protective influence against motor function impairment and neuropathic pain following SCI. This phenomenon may result from the proangiogenetic effect of OPN, possibly due to activation of the VEGF and/or AKT pathways.
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Neuralgia , Osteopontina , Recuperação de Função Fisiológica , Traumatismos da Medula Espinal , Medula Espinal , Animais , Masculino , Camundongos , Angiogênese , Modelos Animais de Doenças , Camundongos Endogâmicos C57BL , Neovascularização Fisiológica/fisiologia , Neovascularização Fisiológica/efeitos dos fármacos , Neuralgia/etiologia , Neuralgia/metabolismo , Neuralgia/prevenção & controle , Osteopontina/metabolismo , Recuperação de Função Fisiológica/fisiologia , Medula Espinal/metabolismo , Traumatismos da Medula Espinal/complicações , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/fisiopatologia , Regulação para Cima , Fator A de Crescimento do Endotélio Vascular/metabolismoRESUMO
Pain management remains among the most common and largely unmet clinical problems today. Local anesthetics play an indispensable role in pain management. The main limitation of traditional local anesthetics is the limited duration of a single injection. To address this problem, catheters are often placed or combined with other drugs in clinical practice to increase the time that local anesthetics act. However, this method does not meet the needs of clinical analgesics. Therefore, many researchers have worked to develop local anesthetic extended-release types that can be administered in a single dose. In recent years, drug extended-release systems have emerged dramatically due to their long duration and efficacy, providing more possibilities for the application of local anesthetics. This paper summarizes the types of local anesthetic drug delivery systems and their clinical applications, discusses them in the context of relevant studies on local anesthetics, and provides a summary and outlook on the development of local anesthetic extended-release agents.
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Anestésicos Locais , Manejo da Dor , Anestesia Local , Analgésicos , Sistemas de Liberação de MedicamentosRESUMO
Fluorescence images enhancement is important as it can provide more information for medical diagnosis. In this work, we design three simple yet useful filters based on the combinations of mathematical functions, which are proved to be effective in strengthening the images acquired from the fluorescence microscope. Using these filters, detailed objects can be found in the dark sections of the fluorescence images. In addition, these filters can be used to enhance the low-light image, which provide satisfactory visual information and marginal profile for the blurred objects in the image. Moreover, these filters have been used to enhance the image with high degradation by the Gaussian noise, where clear edge profile can be extracted. Finally, we have shown that these filters can be utilized for the image compression. Compression ratio can be obtained to be 0.9688. This study shows the making of the filters with dual functions for the image enhancement and the image compression. Our designed filters are showing the potentials in the field of biomedical imaging and pattern identification.
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Silicon anode suffers from rapid capacity decay because of its irreversible volume changes during charging and discharging. As one of the important components of the electrode structure, the binder plays an irreplaceable role in buffering the volume changes of the silicon anode and ensuring close contact between various components of the electrode. Traditional PVDF binder is based on weak van der Waals forces and cannot effectively buffer the stress coming from silicon volume expansion, resulting in rapid decay of silicon anode capacity. In addition, most natural polysaccharide binders with a single force face the same problem due to poor toughness. Therefore, it is extremely important to develop a binder with good force and toughness between the silicon particles. Herein, polyacrylamide (PAM) polymer chains that are premixed homogeneously with various components are cross-linked on-site on the current collector via the condensation reaction with citric acid, forming a polar three-dimensional (3D) network with improved tensile properties and adhesion for both silicon particles and current collector. The silicon anode with the cross-linked PAM binder exhibits higher reversible capacity and enhanced long-term cycling stability; the capacity remains at 1280 mA h g-1 after 600 cycles at 2.1 A g-1 and 770.9 mA h g-1 after being subjected to 700 cycles at 4.2 A g-1. It also exhibits excellent cycle stability in silicon-carbon composite materials. This study provides a cost-effective binder engineering strategy, which significantly enhances the long-term cycle performance and stability of silicon anodes, paving the way for large-scale practical applications.
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The mechanism of neuropathic pain after spinal cord injury is complex, and the communication between neurons, glia, and blood vessels in neurovascular units significantly affects the occurrence and development of neuropathic pain. After spinal cord injury, a domino chain reaction occurs in the neuron-glia-vessel, which affects the permeability of the blood-spinal cord barrier and jointly promotes the development of neuroinflammation. This article discusses the signal transduction between neuro-glial-endothelial networks from a multidimensional point of view and reviews its role in neuropathic pain after spinal cord injury.
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Neuralgia , Traumatismos da Medula Espinal , Humanos , Neuralgia/etiologia , Traumatismos da Medula Espinal/complicações , Neuroglia/fisiologia , Medula Espinal , NeurôniosRESUMO
BACKGROUND: There is an annual increase in the incidence of invasive fungal disease (IFD) of the lung worldwide, but it is always a challenge for physicians to make an early diagnosis of IFD of the lung. Computed tomography (CT) may play a certain role in the diagnosis of IFD of the lung, however, there are no specific imaging signs for differentiating IFD of lung from bacterial pneumonia (BP). METHODS: A total of 214 patients with IFD of the lung or clinically confirmed BP were retrospectively enrolled from two institutions (171 patients from one institution in the training set and 43 patients from another institution in the test set). The features of thoracic CT images of the 214 patients were analyzed on the picture archiving and communication system by two radiologists, and these CT images were imported into RadCloud to perform radiomics analysis. A clinical model from radiologic analysis, a radiomics model from radiomics analysis and a combined model from integrating radiologic and radiomics analysis were constructed in the training set, and a nomogram based on the combined model was further developed. The area under the ROC curve (AUC) of the receiver operating characteristic (ROC) curve was calculated to assess the diagnostic performance of the three models. Decision curve analysis (DCA) was conducted to evaluate the clinical utility of the three models by estimating the net benefit at a range of threshold probabilities. RESULTS: The AUCs of the clinical model for differentiating IFD of lung from BP in the training set and test sets were 0.820 and 0.827. The AUCs of the radiomics model in the training set and test sets were 0.895 and 0.857. The AUCs of the combined model in the training set and test setswere 0.944 and 0.911. The combined model for differentiating IFD of lung from BP obtained the greatest net benefit among the three models by DCA. CONCLUSION: Our proposed nomogram, based on a combined model integrating radiologic and radiomics analysis, has a powerful predictive capability for differentiating IFD from BP. A good clinical outcome could be obtained using our nomogram.
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Micoses , Pneumonia Bacteriana , Humanos , Pulmão/diagnóstico por imagem , Nomogramas , Pneumonia Bacteriana/diagnóstico por imagem , Estudos Retrospectivos , Tomografia Computadorizada por Raios X/métodosRESUMO
In this work, by combining the superiority of polyoxometalates (POMs) and catalytic single-metal site Co of metalloporphyrin, a series of mixed-valence POM-based metal-organic frameworks (MOFs) composites is synthesized by a post-modification method. The electron-transfer property of POM@PCN-222(Co) composite is significantly enhanced owing to the directional electron-transfer from POM to single-metal site Co in PCN-222(Co). In particular, H-POM@PCN-222(Co) gives a high Faradaic efficiency of 96.2% for electroreduction of CO2 into CO and good stability over 10 h. DFT calculations confirm that the directional electron transfer, which accelerates the multi-electron transfer from the electrode to active single-metal site Co, enriches the electron density of the Co center, and ultimately reduces the energy of the rate-determining step, thus increasing the catalytic activity of CO2 reduction reaction (CO2 RR). This work therefore suggests some new insight for the design of efficient electrocatalysts for CO2 RR.
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BACKGROUND: To evaluate the diagnostic performance of apparent diffusion coefficient (ADC) histogram parameters for differentiating the genetic subtypes in lower-grade diffuse gliomas and explore which segmentation method (ROI-1, the entire tumor ROI; ROI2, the tumor ROI excluding cystic and necrotic portions) performs better. MATERIALS AND METHODS: We retrospectively evaluated 56 lower-grade diffuse gliomas and divided them into three categories: IDH-wild group (IDHwt, 16cases); IDH mutant with the intact 1p or 19q group (IDHmut/1p19q+, 18cases); and IDH mutant with the 1p/19q codeleted group (IDHmut/1p19q-, 22cases). Histogram parameters of ADC maps calculated with the two different ROI methods: ADCmean, min, max, mode, P5, P10, P25, P75, P90, P95, kurtosis, skewness, entropy, StDev, and inhomogenity were compared between these categories using the independent t test or Mann-Whitney U test. For statistically significant results, a receiver operating characteristic (ROC) curves were constructed, and the optimal cutoff value was determined by maximizing Youden's index. Area under the curve (AUC) results were compared using the method of Delong et al. RESULTS: The inhomogenity from the two different ROI methods for distinguishing IDHwt gliomas from IDHmut gliomas both showed the biggest AUC (0.788, 0.930), the optimal cutoff value was 0.229 (sensitivity, 81.3%; specificity, 75.0%) for the ROI-1 and 0.186 (sensitivity, 93.8%; specificity, 82.5%) for the ROI-2, and the AUC of the inhomogenity from the ROI-2 was significantly larger than that from another segmentation, but no significant differences were identified between the AUCs of other same parameters from the two different ROI methods. For the differentiaiton of IDHmut/1p19q- tumors and IDHmut/1p19q+ tumors, with the ROI-1, the ADCmode showed the biggest AUC (AUC: 0.784; sensitivity, 61.1%; specificity, 90.9%), with the ROI-2, and the skewness performed best (AUC, 0.821; sensitivity, 81.8%; specificity, 77.8%), but no significant differences were identified between the AUCs of the same parameters from the two different ROI methods. CONCLUSION: ADC values analyzed by the histogram method could help to classify the genetic subtypes in lower-grade diffuse gliomas, no matter which ROI method was used. Extracting cystic and necrotic portions from the entire tumor lesions is preferable for evaluating the difference of the intratumoral heterogeneity and classifying IDH-wild tumors, but not significantly beneficial to predicting the 1p19q genotype in the lower-grade gliomas.
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Neoplasias Encefálicas , Imagem de Difusão por Ressonância Magnética/métodos , Glioma , Interpretação de Imagem Assistida por Computador/métodos , Adulto , Idoso , Área Sob a Curva , Encéfalo/diagnóstico por imagem , Neoplasias Encefálicas/classificação , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/genética , Feminino , Glioma/classificação , Glioma/diagnóstico por imagem , Glioma/genética , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Objective To explore the utility of apparent diffusion coefficient(ADC)histogram analysis for differentiating genetic subtypes of diffuse lower-grade gliomas. Methods A total of 55 patients with WHO grade â ¡/â ¢ diffuse lower-grade gliomas who underwent preoperative routine brain magnetic resonance imaging and diffusion weighted imaging in our center were retrospectively evaluated.Among whom there were 14 patients with isocitrate dehydrogenase(IDH)wild-type gliomas(IDH wt group),19 patients with IDH-mutant 1p19q intact gliomas(IDH mut1p19q int group),and 22 patients with IDH-mutant 1p19q co-deleted gliomas(IDH mut1p19q del group).The whole-lesion ADC values derived from histogram analysis(including ADCmean,ADCminimum,ADC5%,ADC10%,ADC25%,ADC50%,ADC75%,ADC90%,ADC95%,ADCmaximum,mode,range,skewness,kurtosis,standard deviation,inhomogeneity,and entrophy)were measured for each patient.All parameters between the different genetic subtypes were compared by using the Student's t test or Mann-Whitney U test.Receiver operating curve(ROC)analysis was used to assess the diagnostic performance of ADC histogram in distinguishing the different genetic subtypes. Results Compared with IDH wt group,the ADC75%(P=0.021),ADC90%(P=0.015),ADC95%(P=0.014),ADCmaximum (P=0.035),range(P=0.009),standard deviation(P=0.001)and inhomogeneity(P=0.001)were significantly lower in IDH mut group;in contrast,the ADCminimum (P=0.031)and kurtosis(P=0.020)of IDH mut group were significantly higher than those in IDH wt group.The ADCmean(P=0.010),ADC5%(P=0.016),ADC10%(P=0.012),ADC25%(P=0.007),ADC50%(P=0.005),ADC75%(P=0.015),and mode(P=0.002)were significantly higher in IDH mut1p19q int group than in IDH mut1p19q del group.Inhomogeneity achieved the highest area under ROC(AUC)(0.811)in differentiating IDH mut gliomas and IDH wt gliomas,with a cutoff value of 0.229;the sensitivity and specificity were 85.7% and 73.2%.The mode achieved the highest AUC(0.744)in differentiating IDH mut1p19q int gliomas and IDH mut1p19q del gliomas,with a cutoff value was 1448.75×10 -6 mm 2/s;the sensitivity and specificity were 57.9% and 90.9%.Conclusion ADC histograms analysis may be helpful to differentiate genetic subtypes in lower-grade gliomas.
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Neoplasias Encefálicas , Glioma , Imagem de Difusão por Ressonância Magnética , Humanos , Curva ROC , Estudos RetrospectivosRESUMO
The retina is sensitive to injury resulting from oxidative stress (OS) due to its high oxygen consumption. Patients with retinitis pigmentosa suffer from excessive OS. Nacetylcysteine (NAC) is used as a mucolytic agent for the clinical treatment of disorders, such as chronic bronchitis and other pulmonary diseases. The aim of the present study was to investigate the role of hexokinase 2 (HKII) in retinal OS injury. Amyloid ß (Aß)140 was used to establish a cellular model of OS. Cell viability was measured with a Cell Counting Kit8 assay, and the apoptosis, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) of cells were analyzed via flow cytometry with corresponding kits. The mRNA and protein levels were detected by reverse transcriptionquantitative PCR and western blot analyses, respectively. It was observed that Aß140 reduced the expression of HKII in the mitochondria of retinal pigment epithelial ARPE cells and impaired mitochondrial antioxidant functions. Additionally, knockdown of HKII promoted apoptosis, and increased ROS levels and the MMP. NAC attenuated the inhibition of mitochondrial functions induced by Aß140. The knockdown of HKII was revealed to decrease the levels of Bcl2, manganese superoxide dismutase (SOD) and copperzincSOD, and increase the levels of cleaved caspase3, Bax and cytochrome c. The present findings suggested that the dissociation of HKII induced by OS induces apoptosis and mitochondrial damage. This study provided improved understanding of the mechanisms underlying the effects of OS on retinal epithelial cells.
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Hexoquinase/genética , Estresse Oxidativo , Doenças Retinianas/etiologia , Doenças Retinianas/metabolismo , Epitélio Pigmentado da Retina/metabolismo , Peptídeos beta-Amiloides/metabolismo , Peptídeos beta-Amiloides/farmacologia , Apoptose , Biomarcadores , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Técnicas de Inativação de Genes , Hexoquinase/metabolismo , Humanos , Mitocôndrias , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Doenças Retinianas/patologia , Epitélio Pigmentado da Retina/efeitos dos fármacosRESUMO
A high-performance solid-state electrolyte was obtained using porous polybenzimidazole (pPBI) and ionic liquid (IL) (i.e., (1-(3-trimethoxysilylpropyl)-3-methylimidazolium chloride). IL is hydrolyzed to form Si-O-Si networks under acidic conditions, which guarantee the enhanced mechanical properties. The porous structure and Si-O-Si networks improve the acid retention capacity and conductivity simultaneously. The prepared porous composite film exhibits a proton conductivity as high as 0.103 S cm-1 at 170 °C. Then, an all-solid-state supercapacitor (ASSC) was assembled using the obtained film electrolyte and activated carbon electrodes. The electrochemical performance was evaluated at different temperatures (30, 60, 90, 120, and 150 °C). The prepared ASSC displayed a specific capacitance of 85.5 F g-1 at 120 °C, which is 3 times higher than that at 30 °C. Meanwhile, the ASSC displayed excellent long-term cycle stability after 10â¯000 constant current charge and discharge tests, 91.0% capacitance retention, and 95.8% coulomb efficiency. All the results indicate that the porous polymer electrolyte is promising for application in high-temperature energy-storage devices.
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Circular RNAs (circRNAs) are emerging species of mRNA splicing products with largely unknown functions. Although several computational pipelines for circRNA identification have been developed, these methods strictly rely on uniquely mapped reads overlapping back-splice junctions (BSJs) and lack approaches to model the statistical significance of the identified circRNAs. Here, we reported a systematic computational approach to identify circRNAs by simultaneously utilizing BSJ overlapping reads and discordant BSJ spanning reads to identify circRNAs. Moreover, we developed a novel procedure to estimate the P-values of the identified circRNAs. A computational cross-validation and experimental validations demonstrated that our method performed favorably compared to existing circRNA detection tools. We created a standalone tool, CircRNAFisher, to implement the method, which might be valuable to computational and experimental scientists studying circRNAs.
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Biologia Computacional/métodos , RNA/análise , Análise de Sequência de RNA/métodos , Algoritmos , Linhagem Celular Tumoral , Fibroblastos/química , Humanos , RNA/genética , RNA/isolamento & purificação , RNA CircularRESUMO
The previous study has demonstrated that epidermal growth factor (EGF) and EGF receptor (EGFR) signaling plays a critical role in the development of posterior capsule opacification (PCO) through regulating lens epithelial cells (LECs) proliferation. Recent studies have suggested that the residual LECs undergo proliferation and migration, and epithelial-mesenchymal transition (EMT) is the important cause of PCO formation after cataract surgery. EMT of LECs is considered to be playing a central role in the pathogenesis of PCO. In the present study, we investigated whether and how EGF may regulate EMT of LECs. First, we demonstrated that EGF and EGFR signaling induces Myc overexpression in primary human lens epithelial cells (HLECs). In turn, Myc overexpression could inhibit miR-26b by recruitment of HDAC3. Consequently, the downregulated expression of miR-26b increased the expression of EZH2 in primary HLECs. Mechanistically, miR-26b directly controls EZH2 expression by targeting its 3'-UTR in HLECs by luciferase reporter assays. Finally, we demonstrated that EGF induces the expression of EMT markers in primary HLECs via a miR-26b-dependent mechanism. In summary, EGF activated Myc and Myc overexpression inhibited miR-26b by recruitment of HDAC3, which in turn induced the expression of EZH2 and promoted the progression of EMT in HLECs.
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Fator de Crescimento Epidérmico/fisiologia , Transição Epitelial-Mesenquimal , MicroRNAs/metabolismo , Idoso , Movimento Celular , Regulação para Baixo , Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Células Epiteliais/metabolismo , Humanos , Cristalino , Pessoa de Meia-Idade , Proteínas Proto-Oncogênicas c-myc/metabolismoRESUMO
A series of poly (arylene ether ketone sulfone) s containing different amino content (Am-PAEKS) were prepared via direct polycondensation reactions, and then the sulfobutyl groups were grafted onto the Am-PAEKS by amidating reaction between the amide groups in Am-PAEKS and carboxylic acid groups in 4-(N-butane sulfonic) aminobenzoic acid. The structures of the compounds and the polymer were confirmed by FTIR and H-NMR. The new characteristic bands at 1 239 and 1 060 cm(-1) were assigned to O=S=O symmetric stretching vibration and asymmetric stretching vibration of the sulfonic groups in sulfonated poly (arylene ether ketone sulfone) on side chain (S-SPAEKS), and the structures of the polymers were further confirmed by 1H NMR spectra, and the proton peak at 1.64 ppm was assigned to the methyl in the middle of the pendant sulfonated aliphatic side chains, which show that the S-SPAEKS had been prepared successfully. In TGA curves we can observe two distinct weight loss steps, the first step was mainly attributed to the splitting-off of the sulfonic acid groups at 300 degrees C, and the second step was mainly attributed to the decomposition of the main chain of the S-SPAEKS at 450 degrees C. This series of SSPAEKS polymers exhibit excellent thermal properties by thermo gravimetric analysis, which can satisfy the basic requirements of proton exchange membrane (PEM) for fuel cells.
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A series of novel Sulfonted poly(arylene ether sulfone)s (SPAES) containing 1,3,4-oxadiazole are prepared via direct polycondensation reactions to precisely control the degree of sulfonation. The structures of these compounds were confirmed by FTIR, H-NMR and TGA. The characteristic peaks of transmittances spectra of C=N were found at 1 603 cm(-1) and by H-NMR further confirm the structures, which has been successful introducing the oxadiazole ring. In each TGA curve can observe two distinct weight loss steps, which the one at 300 degrees C and the second at 450 degrees C were mainly attributed to the splitting-off of sulfonic acid groups and decomposition of the main chain of the SPAES. The TGA exhibit excellent thermal properties may be satisfied with the basic requirements of proton exchange membrane (PEM) for fuel cells.
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The key to optimizing the properties of molecular scale wires lies in understanding and controlling the solid-state morphologies. This paper examines the influence of oligomer chain length, solvent, and concentration on the formation of nanoscale ribbons on mica substrates from solutions of oligo(p-phenyleneethynylene)s (OPEs) with hexyloxy side chains and thioacetyl end groups. The OPEs are of different molecular chain lengths, in which the numbers ofp-dihexyloxyphenyleneethynylene repeat units, n, are 1, 3, 5, and 7, respectively, with their two ends capped with 4-thioacetylphenyl alligator groups. The atomic force microscope (AFM) is employed to investigate the thin film morphology and study the self-assembled organizations. Solvent and concentration are found to exert a strong influence on thin film morphology. Under suitable conditions, OPEs with 7 p-dihexyloxyphenyleneethynylene repeat units are driven to form micrometer-long nanoribbons, oriented preferably along the 3-fold symmetry axes of the mica substrate. The cross section of the nanoribbons is composed of 7 molecules as evaluated by AFM characterization. On the other hand, oligomers with shorter chain lengths (n = 1, 3, and 5) produce thin films featuring globular nanoaggregates, chains consisting of elongated grains, and rods, respectively. Plausible reasons for the variation in thin film morphology are discussed, based on the results obtained from investigation of oligomer chain length, solvent, and concentration effects. A subtle balance among molecular size and physicochemical properties of solute molecules, solvent molecules, and substrate is crucial for the formation of desired structures. Among them, oligomer chain length plays a key role in thin film morphology, and the critical number of repeat units in OPE/poly(p-phenyleneethynylene) molecules for the formation of nanoribbon structures with a molecular cross section is supposed to be 8 or 9.