Exploring the structural properties and enhancement of Opto-electrical investigations for the synthesized epoxy based polymers with local nanoscale structures

Epoxy networks of the diglycidyl ether of bisphenol A (DGEBA) were prepared using 4, 4′-diaminodiphenyl (44′DDS) and 3, 3′-diaminodiphenyl (33′DDS) sulfone diamines crosslinking hardeners. The structural, linear optical and mechanical properties of the investigated sample were analysed. Dynamic Mechanical Thermal Analysis and wide-angle x-ray diffraction were conducted to select a candidate presenting interesting thermo-mechanical properties and particular nanostructures embedded in an amorphous matrix. Our choice is therefore focused on DGEBA/33′DDS polymer for which, rocking curve measurements revealed the existence of two principal reflecting planes inclined to each other by about 0.27°. To highlight the potential effect of these interfaces, Thermally Stimulated Depolarization Current (TSDC) and Time Domain Spectroscopy measurements have been carried out. The application of the windowing polarization TSDC technique, in DGEBA/33′DDS polymer sample, gives an almost linear variation of the activation energies in the range between 3.65 and 4.09 eV. To our knowledge, this is the first study concerning epoxy polymers in which activation energies associated to ρ interfacial charge relaxations are calculated. To study the effect of the interfaces and trapped charge carriers, correlated by the angle x-ray diffraction measurements, the optical parameters were investigated. Our contribution will open a new avenue for developing the DGEBA/33′DDS polymer sustainable candidate in optoelectronic engineering applications

Synthesis, structural and microstructural study of new FeNa0.5H1.5MoO5 hybrid material for highly efficient energy storage hybrid systems

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Optical, Dielectric Properties and Energy Storage Efficiency of ZnO/Epoxy Nanocomposites

International audienceZnO/epoxy nanocomposites were prepared in five different contents (0.25–3.0 wt%). Optical, thermal and dielectric properties have been examined as a function of ZnO nanoparticles. The absorption optical spectra exhibit a broad intense peak assigned to the n–π* (HOMO–LUMO) transitions. Nanocomposite with 3.0 wt% ZnO sample completely blocks UV-light radiations in the region from 300 to 480 nm, which allowed that the prepared material to be used for UV-Shielding devices. The optical band gap is found to decrease with increasing filler ZnO concentrations. This might be due to increasing the density of defect states. Permittivity and electric modulus formalisms are used to analyze and interpret the experimental data. γ relaxation is observed in the low temperature region, which is attributed to the rearrangement of small parts of the polymeric chains. The α relaxation and the Maxwell–Wagner–Sillars (MWS) effect, attributed to the glass rubber transition of the polymeric matrix and the interfacial polarization phenomena respectively, are observed in the high temperature region. Using Havriliak–Negami approach, the temperature dependence of relaxation time for MWS and γ relaxations follows an Arrhenius behavior while the α relaxation time is well described by the Vogel–Fulcher–Tamann behavior. The activation energies of all relaxation modes were calculated and discussed. The energy density of the investigated samples is significantly enhanced. It is about 2 × 10−6 J/m3 for nanocomposite with 3.0 wt% ZnO at 20 °C.These results indicate that the effect of ZnO nanoparticles makes the proposed materials suitable candidates for energy storage applications

Study of AC electrical conduction mechanisms in an epoxy polymer

International audienceThe AC conductivity of an epoxy resin was investigated in the frequency range 10−1−106 Hz at temperatures ranging from -100 to 120 °C. The frequency dependence of σac was described by the law: σac=ωε0ε′′HN+Aωs. The study of temperature variation of the exponent (s) reveals two conduction models: the AC conduction dependence upon temperature is governed by the small polaron tunneling mechanism (SPTM) at low temperature (-100 -60 °C) and the correlated barrier hopping (CHB) model at high temperature (80-120 °C)

A comparative study of structural and dielectric properties of diglycidyl ether of bisphenol A (DGEBA) cured with aromatic or aliphatic hardeners

International audienceThis study aims to present structural and dielectric comparisons between two epoxy polymers. These polymers are realized by curing diglycidyl ether of bisphenol A (DGEBA) resin with either aliphatic 1,3-diaminopropane (PDA) or aromatic 4,4′-diaminodiphenyl sulfone (DDS) hardeners. They are called DGEBA/PDA and DGEBA/DDS. Several complementary techniques have been used in the present study. The structural analysis was performed using grazing incidence X-ray reflectometry. It reveals the presence of a locally ordered nanostructure in the DGEBA/DDS polymer and an amorphous character for the DGEBA/PDA one. Dielectric characterization was carried by means of dielectric relaxation spectroscopy (DRS), thermally stimulated depolarization current (TSDC) and time domain spectroscopy (TDS). DRS measurements performed over wide ranges of temperature (−80 to 160 °C) and frequency (10−1–106 Hz) showed the presence of dipolar γ and α relaxations in both polymers. Nevertheless, the interfacial Maxwell–Wagner–Sillars (MWS) relaxation appeared only in DGEBA/DDS. This can be related to the local nanostructure within this polymer, which can give rise to interfaces. Relaxation parameters were deduced from the best fits of experimental data with the Havriliak–Negami model. The calculated fragility index indicates that DGEBA/DDS is more fragile than DGEBA/PDA. The loss factor ε′′(f) was calculated from the isothermal discharging current measurements, using Hamon approximation. Thanks to this ε′′ calculation an interfacial relaxation was revealed in the frequency range of 10−3–10−1 Hz for each investigated polymer

Effects of curing agent on conductivity, structural and dielectric properties of an epoxy polymer

International audienceTwo epoxy polymers were prepared by curing the diglycidyl ether of bisphenol A (DGEBA) epoxy resin with two hardeners: the ethylenediamine (EDA) and the 3,3′-diaminodiphenyl sulfone (33′DDS) which are respectively aliphatic and aromatic. Structural properties of DGEBA/EDA and DGEBA/33′DDS polymers were investigated by means of grazing incidence X-ray reflectometry. Their dielectric properties were studied using the dielectric relaxation spectroscopy (DRS) over wide ranges of temperature (from −80 to 200 °C) and frequency (from 10−1–106 Hz), and thermally stimulated depolarization current (TSDC) technique. X-ray data revealed the presence of a locally periodic nanostructure in polymer cured with the aromatic hardener (DGEBA/33′DDS). γ and α dipolar relaxations were highlighted for the two polymers while the Maxwell–Wagner–Sillars (MWS) relaxation appears only in the DGEBA/33′DDS. The electric modulus data were fitted using Havriliak–Negami approch. Conductive properties of epoxies were investigated. Ac conductivity data reveal that DGEBA/EDA is more conductive than the DGEBA/33′DDS

Autoimmune diseases association study with the KIAA1109–IL2–IL21 region in a Tunisian population

This deposit is composed by a publication in which the IGC's authors have had the role of collaboration (it's a collaboration publication). This type of deposit in ARCA is in restrictedAccess (it can't be in open access to the public), and can only be accessed by two ways: either by requesting a legal copy from the author (the email contact present in this deposit) or by visiting the following link: https://link.springer.com/article/10.1007%2Fs11033-014-3596-5This deposit is composed by the main article plus the supplementary materials of the publication.This publication hasn't any creative commons license associated.Further funders are not indicated in the document.Autoimmune diseases (ADs) share several genetic factors resulting in similarity of disease mechanisms. For instance polymorphisms from the KIAA1109-interleukin 2 (IL2)-IL21 block in the 4q27 chromosome, has been associated with a number of autoimmune phenotypes. Here we performed a haplotype-based analysis of this AD related region in Tunisian patients. Ten single nucleotide polymorphisms (rs6534347, rs11575812, rs2069778, rs2069763, rs2069762, rs6852535, rs12642902, rs6822844, rs2221903, rs17005931) of the block were investigated in a cohort of 93 systemic lupus erythematosus (SLE), 68 ulcerative colitis (UC), 39 Crohn's disease (CD) patients and 162 healthy control subjects of Tunisian origin. In SLE population, haplotypes AGCAGGGTC, AGAAGAGTC, AGAAGGGTC and AGCCGAGTC provided significant evidence of association with SLE risk (p = 0.013, 0.028, 0.018 and 0.048, respectively). In the UC population, haplotype AGCCGGGTC provided a susceptibility effect for UC (p = 0.025). In the CD population, haplotype CAGGCC showed a protective effect against the development of CD (p = 0.038). Haplotype AAGGTT provided significant evidence to be associated with CD risk (p = 0.007). Our results support the existence of the associations found in the KIAA1109/IL2/IL21 gene region with ADs, thus confirms that the 4q27 locus may contribute to the genetic susceptibility of ADs in the Tunisian population.This work was supported by a grant from the «Ministère de la recherche Scientifique et de la recherche scientifique» (Tunisia). Genotyping was supported by the Instituto Gulbenkiande Ciência, Oeiras, Portugal.info:eu-repo/semantics/publishedVersio

Tunisian Pistachio Hull Extracts: Phytochemical Content, Antioxidant Activity, and Foodborne Pathogen Inhibition

The present study aimed to discriminate pistachio (Pistacia vera L.) hulls belonging to three different Tunisian geographical origins and extracted separately by hexane, acetone, acetonitrile, and water in terms of phytochemicals and antioxidant and antibacterial activities using multivariate analysis. Significant differences (P<0.05) in the phytochemical content, antioxidant, and antifoodborne bacterial activities were detected among the pistachio hulls populations. Pearson correlation, principal component analysis (PCA), hierarchical cluster analysis (HCA), and heat map were used to distinguish the relationship between the different regions on the basis of the biological activities. It was found that the twelve (4 extracts × 3 geographical sources) pistachio hulls extracts could be classified geographically into four distinct groups. To explore the mode of action of the aqueous pistachio hull extract against L. monocytogenes and S. enterica, polymyxin acriflavine lithium chloride ceftazidime aesculin mannitol (PALCAM) and xylose lysine deoxycholate (XLD) broth media were artificially contaminated at 104 CFU/mL. Using linear and general linear models, aqueous pistachio hull extract was demonstrated to control the two dominant food-borne pathogens by suppressing the bacterial growth

Exploring the optical and dielectric properties of bifunctional and trifunctional epoxy polymers

Two polymers were prepared from diglycidyl ether of bisphenol A (DGEBA) and triglycidyl p-aminophenol (TGAP) epoxy resins, using the same hardener diethylenetriamine (DETA). The obtained polymers were compared in terms of structural, optical, mechanical, thermal and dielectric properties. Dielectric spectroscopy and dynamic mechanical analysis indicated the presence of dipolar dielectric relaxations in both polymers, and interfacial one only for TGAP/DETA, which is consistent with XRD findings. Different approaches were considered to fit electrical modulus and conductivity and to estimate the relaxation times and activation energies according to temperature. For optical measures, a novel result processing approach is proposed for an accurate determination of the polymers bandgap and for highlighting the existence of additional energy transition level for TGAP. Results indicate that this polymer could be a potential candidate for use as a protective film and as UV/blue-light filter for screens and window

A Review on Worldwide Ephedra History and Story: From Fossils to Natural Products Mass Spectroscopy Characterization and Biopharmacotherapy Potential

Growing worldwide, the genus Ephedra (family Ephedraceae) had a medicinal, ecological, and economic value. The extraordinary morphological diversity suggests that Ephedra was survivor of an ancient group, and its antiquity is also supported by fossil data. It has recently been suggested that Ephedra appeared 8–32 million years ago, and a few megafossils document its presence in the Early Cretaceous. Recently, the high analytical power provided by the new mass spectrometry (MS) instruments is making the characterization of Ephedra metabolites more feasible, such as ephedrine series. In this regard, the chemical compounds isolated from crude extracts, fractions, and few isolated compounds of Ephedra species were characterized by MS-based techniques (LC-MS, LC-ESI-MS, HPLC-PDA-ESI/MS, LC-DAD-ESI/MSn, LC/Orbitrap MS, etc.). Moreover, we carry out an exhaustive review of the scientific literature on biomedicine and pharmacotherapy (anticancer, antiproliferative, anti-inflammatory, antidiabetic, antihyperlipidemic, antiarthritic, and anti-influenza activities; proapoptotic and cytotoxic potential; and so on). Equally, antimicrobial and antioxidant activities were discussed. This review is focused on all these topics, along with current studies published in the last 5 years (2015–2019) providing in-depth information for readers