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In this article, chitosan copper oxide nanocomposite was synthesized by the solution casting method under microwave irradiation. The nanocomposite solution was microwave irradiated at 300 watt for 3 min under optimal irradiation conditions. By suppressing particle agglomeration, the chitosan matrix was successfully used as a metal oxide stabilizer. The goal of this research was to create, characterize, and test the catalytic potency of these hybrid nanocomposites in a number of well-known organic processes. The prepared CS-CuO nanocomposites were analyzed by different techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Moreover, energy-dispersive X-ray spectroscopy (EDS) was used to measure the copper content in the prepared nanocomposite film. The finger-print peaks in the FTIR spectrum at around 632–502 cm−1 confirmed the existence of the CuO phase. The CS-CuO nanocomposite has been shown to be an efficient base promoter for nitroolefin synthesis via the nitroaldol reaction (Henry reaction) in high yields. The reaction variables were studied to improve the catalytic approach. Higher reaction yields, shorter reaction times, and milder reaction conditions are all advantages of the technique, as is the catalyst’s reusability for several uses.

Calcium oxide (CaO) nanoparticles have recently gained much interest in recent research due to their remarkable catalytic activity in various chemical transformations. In this article, a chitosan calcium oxide nanocomposite was created by the solution casting method under microwave irradiation. The microwave power and heating time were adjusted to 400 watts for 3 min. As it suppresses particle aggregation, the chitosan (CS) biopolymer acted as a metal oxide stabilizer. In this study, we aimed to synthesize, characterize, and investigate the catalytic potency of chitosan–calcium oxide hybrid nanocomposites in several organic transformations. The produced CS–CaO nanocomposite was analyzed by applying different analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM). In addition, the calcium content of the nanocomposite film was measured using energy-dispersive X-ray spectroscopy (EDS). Fortunately, the CS–CaO nanocomposite (15 wt%) was demonstrated to be a good heterogeneous base promoter for high-yield thiazole production. Various reaction factors were studied to maximize the conditions of the catalytic technique. High reaction yields, fast reaction times, and mild reaction conditions are all advantages of the used protocol, as is the reusability of the catalyst; it was reused multiple times without a significant loss of potency.

Recently, Strontium oxide (SrO) nanoparticles (NPs) and hybrids outperformed older commercial catalysts in terms of catalytic performance. Herein, we present a microwave-assisted easy in situ solution casting approach for the manufacture of strontium oxide nanoparticles doped within a naturally occurring polymer, chitosan (CS), at varying weight percentages (2.5, 5, 10, 15, and 20 wt.% SrO/chitosan). To construct the new hybrid material as a thin film, the produced nanocomposite solutions were cast in petri dishes. The aim of the research was to synthesize these hybrid nanocomposites, characterize them, and evaluate their catalytic potential in a variety of organic processes. The strontium oxide-chitosan nanocomposites were characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques. All the results confirmed the formation of chitosan–strontium oxide nanocomposite. FTIR spectrum of nanocomposite showed the presence of a characteristic peak of Sr-O bond. Furthermore, XRD revealed that SrO treatment increased the crystallinity of chitosan. The particle size was calculated using the Debye–Scherrer formula, and it was determined to be around 36 nm. The CS-SrO nanocomposite has been proven to be a highly efficient base promoter for the synthesis of 2-hydrazono [1,3,4]thiadiazole derivatives. To optimize the catalytic method, the reaction factors were investigated. The approach has various advantages, including higher reaction yields, shorter reaction durations, and milder reaction conditions, as well as the catalyst’s reusability for several applications.

Calcium oxide (CaO) nanoparticles have recently gained much interest in recent research due to their remarkable catalytic activity in various chemical transformations. In this article, a chitosan calcium oxide nanocomposite was created by the solution casting method under microwave irradiation. The microwave power and heating time were adjusted to 400 watts for 3 min. As it suppresses particle aggregation, the chitosan (CS) biopolymer acted as a metal oxide stabilizer. In this study, we aimed to synthesize, characterize, and investigate the catalytic potency of chitosan-calcium oxide hybrid nanocomposites in several organic transformations. The produced CS-CaO nanocomposite was analyzed by applying different analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM). In addition, the calcium content of the nanocomposite film was measured using energy-dispersive X-ray spectroscopy (EDS). Fortunately, the CS-CaO nanocomposite (15 wt%) was demonstrated to be a good heterogeneous base promoter for high-yield thiazole production. Various reaction factors were studied to maximize the conditions of the catalytic technique. High reaction yields, fast reaction times, and mild reaction conditions are all advantages of the used protocol, as is the reusability of the catalyst; it was reused multiple times without a significant loss of potency.

Chitosan (CS) was used as a powerful chelating agent and an excellent template for synthesis of metal oxide nanoparticles (NPs). The CS-MgO nanocomposite film was prepared by adding 10%wt of MgO relative to CS and was characterized by different techniques. From the FTIR, some of the main characteristic peaks of CS were shifted due to the interaction with MgO especially with OH and NH2 groups. Also, SEM graphs showed a clear change in the morphological surface of CS. Moreover, XRD pattern shows an improvement in the crystallinity due to incorporation of MgO NPs. The dielectric and optical properties of the nanocomposite film were studied. Moreover, the effect of temperature on the dielectric properties of the hybrid film was studied. The absorption and transmittance were measured for the prepared samples by using UV–VIS spectrophotometer. The optical parameters such as refractive index, absorption coefficient and energy band gap for the CS-MgO nanocomposite were calculated and compared with the pure CS film only.

In recent years, nanotechnology has become a considerable research interest in the area of preparation of nanocatalysts based on naturally occurring polysaccharides. Chitosan (CS), as a naturally occurring biodegradable and biocompatible polysaccharide, is successfully utilized as an ideal template for the immobilization of metal oxide nanoparticles. In this study, zinc oxide nanoparticles have been doped within a chitosan matrix at dissimilar weight percentages (5, 10, 15, 20, and 25 wt.% CS/ZnO) and have been fabricated by using a simple solution casting method. The prepared solutions of the nanocomposites were cast in a Petri-dish and were subsequently shaped as a thin film. After that, the structural features of the nanocomposite film have been studied by measuring the FTIR, SEM, and XRD analytical tools. FTIR spectra showed the presence of some changes in the major characteristic peaks of chitosan due to interaction with ZnO nanoparticles. In addition, SEM graphs exhibited dramatic morphology changes on the chitosan surface, which is attributed to the surface adsorption of ZnO molecules. Based on the results of the investigated organic catalytic reactions, the prepared CS/ZnO nanocomposite film (20 wt.%) could be a viable an effective, recyclable, and heterogeneous base catalyst in the synthesis of thiazoles. The results showed that the nanocomposite film is chemically stable and can be collected and reused in the investigated catalytic reactions more than three times without loss of its catalytic activity.

Chitosan/magnesia hybrid films (CS-Mg) have been prepared via sol-gel process and employed as heterogeneous catalysts. An in situ generation of a magnesia network in the chitosan matrix was performed through hydrolysis/condensation reactions of magnesium ethoxide. The synthesized hybrid films were characterized using various analytical techniques, such as X-ray photo-electron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The hybrid films display excellent catalytic activities in Michael and Knoevenagel reactions via one pot or solvent-free approaches under microwave irradiation conditions. Chitosan/magnesia hybrid films, catalysed pyrimidine, benzochromene, coumarin and arylidene-malononitriles derivatives formation reactions occurred with highly efficient yields of 97%, 92%, 86% and 95% respectively. Due to the fact that the films are durable and insoluble in common organic solvents, they were easily separated and can be recycled up to five times without a considerable loss of their catalytic activity.

Copper oxide-chitosan nanocomposite was synthesized simply via simple solution casting method and was characterized by different analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and Thermogravimetric analysis (TGA). The copper oxide content in the prepared nanocomposite film was estimated from the Energy-dispersive X-ray spectroscopy (EDS) and the copper content in the sample was found to be 12.57 wt%. From the XRD pattern, the average particle size was calculated using Debye-Scherrer formula and was found to be 33.5 nm. The TGA curves showed that the thermal stability of the hybrid nanocomposite was found to be superior to the native CS, which is attributed to the existence of the thermally stable CuO. The chitosan/CuO nanocomposite has proven to be an excellent heterogeneous base catalyst for regioselective 1,3-dipolar cycloaddition of hydrazonoyl chlorides 1a-j with enamine 2 to give 1,3,4-trisubstituted pyrazoles 3a-j in excellent yields. The performance of the nanocomposite was optimized by varying several reaction conditions.

Chitosan copper (II) oxide nanocomposite was synthesized, characterized and used to synthesize [1,2,3]triazoles. Nanocomposite was characterized by using FTIR, XRD, FESEM, and EDS techniques, which reflected rough morphology. The powerful catalytic activity of hybrid nanocomposite was utilized to synthesize chalcones (3a-p) in relatively high yields (82%-98%) and multicomponent regio-selective cycloaddition of chalones, aryl halides (4), and sodium azide to afford the expected N-2-aryl[1,2,3]triazoles (5a-h) (80%-95% yield) rather than N-1-aryl[1,2,3]-triazoles (6a-h). The performance of nanomaterial was optimized by several variables. The capability of the nanocomposite was compared with previous work and the nanocomposite was found more efficient, economic and reproducible. The hybrid nanocomposite could be easily isolated form the reaction mixture and recycled four times without any significant loss of its catalytic activity. The reported catalyst is an inexpensive for good yields of the triazoles and may be used at industrial production for the reported compounds.

The objective of this study is to simulate and predict the thermomechanical damage of composite material assemblies subjected to impact load while in a high temperature environment. Three-dimensional models were developed for a glass-fiber reinforced vinyl ester double-lap bonded composite assembly subject to combined mechanical and high thermal loads . Both thermal and mechanical models were implemented in the finite element analysis software Abaqus , using sequential heat transfer and dynamic implicit simulations. The thermal model is customized to properly simulate the thermal behavior of composites and generate accurate results while the mechanical model uses the existing functions of Abaqus. For a double-lap composite assembly, thermomechanical failure is predicted in the adhesive zone, at the adherent/adhesive interface, as the adhesive deteriorates at the early stages of exposure. The adherent also deteriorates but at a slower rate. Furthermore, stress concentration is observed at the edges of the stress distribution along the adhesive length, while the average stress along the length decreases gradually as a function of the fire exposure time. The conducted simulations made it possible to predict the stress distribution field variation as a function of time in the double-lap bonded assembly under a combined thermal-impact load. This would serve as a valuable tool for composite structure designers in sizing bonded composite assemblies for their structural projects, as the specifications for certain structures impose a time of evacuation of the structure during a shock and triggering of a fire.

Recently, the development of nanocatalysts based on naturally occurring polysaccharides has received a lot of attention. Chitosan (CS), as a biodegradable and biocompatible polysaccharide, is considered to be an excellent template for the design of a hybrid biopolymer-based metal oxide nanocomposite. In this case, lanthanum oxide nanoparticles doped with chitosan at different weight percentages (5, 10, 15, and 20 wt% CS/La2O3) were prepared via a simple solution casting method. The prepared CS/La2O3 nanocomposite solutions were cast in a Petri dish in order to produce the developed catalyst, which was shaped as a thin film. The structural features of the hybrid nanocomposite film were studied by FTIR, SEM, and XRD analytical tools. FTIR spectra confirmed the presence of the major characteristic peaks of chitosan, which were modified by interaction with La2O3 nanoparticles. Additionally, SEM graphs showed dramatic morphological changes on the surface of chitosan, which is attributed to surface adsorption with La2O3 molecules. The prepared CS/La2O3 nanocomposite film (15% by weight) was investigated as an effective, recyclable, and heterogeneous base catalyst in the synthesis of pyridines and pyrazoles. The nanocomposite used was sufficiently stable and was collected and reused more than three times without loss of catalytic activity.

A series of high temperature alkyl and alkoxy biphenyltetracarboxydiimide liquid crystals have been prepared under ball mill method using solvent-free mechanochemical approach. The thermal properties of the prepared compounds were investigated by deferential scanning calorimetry (DSC) measurements and the textures were identified by polarized optical microscope (POM). The compounds showed smectic mesomorphic behaviour. The results showed the increasing nature of transition temperature Cr-SmC with chain length with increments of the SmC mesophase range. However, the mesophase range of the SmA was decreased with the terminal chain length either for the alkyl or alkoxy terminal groups. Moreover, the DFT theoretical calculations have been conducted give a detailed projection of the structure of the prepared compounds. A conformational investigation of the biphenyl part has been studied. A deep illustration of the experimental mesomorphic behaviour has been discussed in terms of the calculated aspect ratio. A projection of the frontier molecular orbitals as well as molecular electrostatic potential has been studied to show the effect of the polarity of the terminal chains on the level and the gab of the FMOs and the distribution of electrostatic charges on the prepared molecules.

In this work, the elasticity constants of anisotropic thin films were determined using a model developed specifically in order to use the Impulse Excitation Technique (IET). The model is based on the lamination theory and was validated with a finite element analysis. The IET was used in flexural and torsional vibration modes in order to determine the Young's and shear moduli of coatings. The anisotropic behavior was evaluated for titanium thin films deposited by magnetron sputtering at Glancing Angle Deposition (GLAD) on glass substrates and silicon wafers. The elastic response was examined for three different glancing angles and the presence of in-plane anisotropy of the film was noticed from the measured elasticity constants. The difference between conventional and GLAD sputtering was evaluated in terms of microstructure, texture evolution and elastic properties. The influence of the film porosity on the elasticity constants was investigated. Nanoindentation measurements were performed in order to evaluate the effect of the glancing angle on the hardness and the reduced modulus. The results revealed that the elasticity constants of the titanium thin film were mostly affected by the glancing angle and they decreased when the glancing angle increased. The same effect was noticed for the film hardness and reduced modulus. Upon increasing the glancing angle, the film anisotropy was increased owing to different factors, among which the non-standard columnar growth and the inclined crystallites toward the vapor flux direction.

The vascular endothelial growth factor receptor 2 (VEGFR2) is considered as a significant target for inhibition in the discovery of novel molecules with anti-proliferative activity. Here, we report the synthesis of novel derivatives of 1,2,4-triazole as potent VEGFR2 inhibitors with anti-HCC activity. The chemical structures of the target triazole derivatives were assured through elemental and spectral analysis. The in vitro anti-VEGFR2 activity of the new compounds was evaluated. Most compounds revealed promising inhibitory activity in comparison to Sorafenib (IC50= 0.088 µM). The triazolothiadiazine derivative 7a was the most active one (IC50= 0.057 µM). Also, the phenylhydrazono triazole derivatives 11c, 13b, and 13c showed potent activities (IC50= 0.074–0.124 µM) that were comparable to that of Sorafenib. Moreover, the anti-proliferative activity of most active compounds was assessed against two HCC cell lines and against normal hepatic cells THLE3. Compound 7a showed superior activity to Sorafenib; 2 times its activity against HepG2 and 15.5 times against Huh7. Furthermore, compound 13c was comparable to sorafenib against HepG2 and 4.1 times against Huh7. Besides, these potent compounds displayed higher safety profiles than Sorafenib against the normal THLE3 cells. In addition, docking simulation demonstrated good fitting with strong binding interactions within the VEGFR2 ATP binding site. In silico ADME calculations showed good GI absorption and high oral bioavailability of compound 7a.

In this paper deep investigations and full characterization of SA 70 epoxy's properties as a bulk material and as an adhesive in a bonded assembly, are performed. Those properties are essential for an industrial or a supplier and whose determination is not at all obvious. Double lap bonded steel-SA 70 epoxy assemblies were prepared and then thermally aged within a wide interval of temperatures up to 370 °C. The thickness of the central adherend was kept always equal to twice the thickness of each of the upper and lower adherend. Ethanol and sand blasting were the two surface treatments adopted for the substrates while three different central adherend thicknesses from each surface treatment were prepared. Preliminary investigations were performed through thermogravimetric analysis (TGA) tests applied on cured SA70 epoxy specimens and this for the whole ageing temperatures range; showing that the onset temperature for this adhesive is around 380 °C and a major mass loss occurs at 420 °C. Isothermal TGAs were performed at 300 °C, 350 °C and 370 °C in order to choose ageing duration. The aged specimens were then tested under impact at 10 m/s using the Split Hopkinson Pressure Bar (SHPB) technique. It was found that the sand blasted specimens exhibit higher shear strength. No clear effect of substrates’ thicknesses on the joint shear strength was noticed. In addition, the evolution of the shear strength with the ageing temperature was found to be in line with the TGA results: the strength increases with the ageing temperature up to 200 °C; after 225 °C the strength decreases. From 300 °C and above the strength drops drastically.

The main objective of the present study was to develop a fire thermal model able to predict the evolution of the temperature gradient across a sandwich composite structure when exposed to fire. Thermal response of sandwich panels, with glass/polyester skins and balsa core, was investigated under severe temperature conditions as samples were exposed to high temperatures up to 570 °C. Based on experimental measurements, an accurate three-dimensional thermal model was developed using finite element analysis . The obtained predictions of the temperature field are in excellent agreement with the experimental data, showing the importance of combined numerical-experimental analyses. This allowed us to propose a new approach that can be used for the prediction of thermo-mechanical post-combustion properties in a very large number of fire and material scenarios according to its simplicity and robustness.

This work aims at highlighting some microstructure-properties relationships; namely: the effect of the microstructure on the diffusive behavior of composites tubes obtained by filament winding technique. Composites tubes are made from either glass or carbon fibers impregnated with the same epoxy matrix cured at 150℃. Specimens were rings cut from tubes. Three winding angles were investigated: ± 42°, ±56° or ±78°. Glass and carbon/epoxy tubes present a strongly different void content, respectively, 1.7% and 5.7%. Immersion aging tests were conducted in distilled water at 70℃. Results show that despite both glass and carbon composites are made of the same resin, moisture uptake exhibits strong discrepancies between glass/epoxy and carbon/epoxy samples. An investigation of the most appropriate diffusion model for glass and carbon/epoxy specimens is developed in this paper, based on an experimental study of the microstructure of these composites owing to various complementary characterization methods. Glass/epoxy rings exhibit a Fickian diffusion, whereas carbon/epoxy specimens do not match a Fickian diffusion. A dual-stage Fickian law is discussed and seems to fit quite well in experimental observations.

International audience; This work presents a methodology to determine the Young's modulus of an individual coating in a multilayered system by means of the Impulse Excitation Technique (IET). In this technique, the composite beam is excited by an impulse and the frequencies of the first four bending modes are extracted. They are used in a one-dimensional model to obtain the Young's modulus of the coating. Based on two different theories: the Flexural Rigidity of a Composite Beam (FRCB) and the Classical Laminated Beam Theory (CLBT), different models proposed in the literature for bilayer beams have been extended to describe a beam composed of N dissimilar layers. Moreover, an enhanced model was developed based on the laminated theory. It takes into account the shift of the neutral axis after each deposited film, which makes it applicable for any film thickness. The reliability of the proposed model is investigated by comparing its predicted frequency to those of existing models for bilayers. It is also compared to finite element analysis of beams composed of two and three dissimilar layers. A metrological study was performed to quantify the most influencing factors on the global uncertainty. The methodology was applied to beams composed of three layers (N = 3) with titanium and niobium thin films deposited by DC magnetron sputtering. The most accurate models are applied to obtain the Young's modulus of Ti and Nb films in the Ti/Nb/(AISI 316 or Glass) multilayer beam. The films microstructure and morphology were analyzed by X-ray diffraction and scanning electron microscopy.

The authors were concerned in this work in examining the influence of many mechanical and geometrical parameters on the mode shapes of vibration of a double-lap bonded joint. The parameters varied in this study were: adhesive Young’s modulus, adhesive and adherents’ thicknesses and overlap length. The substrates were made from steel; the adhesive is an epoxy resin. The study was carried out using ANSYS Finite Element software where the first ten modes were extracted. The results obtained from an experimental test conducted by the same workgroup were used to validate the numerical results. Based on the numerical parametric study, the results have shown a dominant influence of the substrates’ thickness and the overlap length: the natural frequency increases remarkably with those two parameters. Moreover, the frequencies of the first ten modes were found to be very sensitive in increasing with the increment of either the adherents’ thicknesses or the overlap length. On the other hand, the influence of the adhesive Young’s modulus was found to be very slight on increasing the natural frequencies for all modes while the adhesive thickness was found to have quite no influence for the first couple of modes, with a slight decrement of frequency for higher modes. Finally, by setting the latter parameters to reference values, a unified parameter function of overlap length and adherent thickness was defined and approximated, and analytical relations for natural frequencies of the first ten modes were established.

Chitosan-aluminum oxide nanocomposite was synthesized, characterized, and used as a green heterogeneous catalyst to synthesize novel imidazopyrazolylthione derivatives. Nanocomposite polymeric material was characterized by EDS-SEM and XRD. The powerful catalytic activity, and its base character of the nanocomposite, was used to synthesize imidazopyrazolylthione (1) in a good yield compared to traditional cyclocondensation synthesis. Using the nanocomposite catalyst, substitution of the thiol group (1) afforded the corresponding thiourea (2) and the corresponding ester (3). The efficiency of the nanocomposite over the traditional base organic catalyst, Et3N and NaOH, makes it an effective, economic, and reproducible nontoxic catalyst. Moreover, the heterogeneous nanocomposite polymeric film was easily isolated from the reaction medium, and recycled up to four times, without a significant loss of its catalytic activity. The newly synthesized derivatives were screened as antibacterial agents and showed high potency. Molecular docking was also performed for a more in-depth investigation. The results of the docking studies have demonstrated that the docked compounds have strong interaction energies with both Gram-positive and Gram-negative bacteria.

This work examines the influence of engineering constants except the in-plane longitudinal Young's modulus of composite substrates on the behavior of a double lap bonded joint subjected to dynamic shear load using numerical simulations. The longitudinal Young's modulus was kept constant by varying the fibers' volume fractions and distributions. Three fibers' distributions were investigated: unidirectional laminates, in-plane bidirectional laminates, and fibers woven along the three orthogonal axes. It was found that the stress homogeneity was not affected remarkably by the fibers' distribution while the maximum average shear stress increases with the increase of substrates in-plane shear stiffness.

Adhesive bonding of structural composite structures is increasingly used in several engineering applications. The mechanical behavior of adhesively-bonded composite joints is highly influenced by the reinforcements’ orientations. In this work, the influence of composite laminates’ orientation, on the peel and shear stresses in the adhesive layer of composite double lap joints subjected to in-plane impact loading, was investigated. To this end, three-dimensional finite elements analysis was undertaken. First, four laminate orientations/configurations were considered: 0°, ±45°, 90°, 0/90°. Second, configurations were chosen in a manner to explore the influence of plies’ positions. Starting from the 0°, one or two ply(ies) are replaced by one or two ply(ies), respectively, which are oriented in 90° or ±45° directions. It was found that the profile of the substrates and adhesive stresses variation along the axial/longitudinal direction is not affected by the substrates orientations. However, the highest adhesive stresses are achieved when fibers are all or mostly oriented along the loading/axial direction [0°] and the lowest adhesive stresses are obtained when the fibers are oriented perpendicular to the applied load [90°]. It is then concluded that the adhesive stresses increase as the substrates longitudinal stiffness increases. It is also concluded that the stress in the adhesive layer is mostly influenced by the closest laminate plies and almost not affected by the far plies.

Chitosan-g-poly(2-cyano-1-(pyridin-3-yl)allyl acrylate) (Cs-g-PCPA), having a grafting percentage (G%) of 64%, was prepared and was then subjected to complexation with iron(III) (Cs-g-PCPA/Fe(III)). The results of the catalytic studies demonstrated that Cs-g-PCPA serves as an efficient, recyclable and eco-friendly, basic catalyst for Michael addition reactions, which produce adducts in high yields under mild conditions. Moreover, a Cs-g-PCPA-supported iron(III) complex was prepared and was then characterized by using FESEM, XRD, TGA, and XPS. In addition, the EDS plot of the Fe(III) chelate confirms the presence of a relatively high amount (13%) of Fe(III). The Cs-g-PCPA (G% = 64)-supported iron(III) complex (Cs-g-PCPA/Fe(III)) in the presence of H2O2 can be used to oxidize methyl pyridazinyl carbonitriles to form the corresponding fused furan derivatives efficiently. These polymeric catalysts are stable such that they can be recycled and reused more than five times without losing their catalytic activity.

2-(1-{4-[(4-Methylphenyl)sulfonamido]phenyl}ethylidene)thiosemicarbazide (3) was exploited as a starting material for the synthesis of two novel series of 5-arylazo-2-hydrazonothiazoles 6a - 6j and 2-hydrazono[1,3,4]thiadiazoles 10a - 10d, incorporating sulfonamide group, through its reactions with appropriate hydrazonoyl halides. The structures of the newly synthesized products were confirmed by spectral and elemental analyses. Also, the antimicrobial, anticancer, and DHFR inhibition potency for two series of thiazoles and [1,3,4]thiadiazoles were evaluated and explained by molecular docking studies and SAR analysis.

The main target of this paper is to investigate the effect of peak stress at the extremities of the adhesive layer of a bonded assembly subjected to dynamic shear impact. It is known, that under both static and dynamic loadings such joints endure at their extremities high level of stresses, an aspect known as edge effects. Double lap joint assembly was considered with unidirectional carbon–epoxy substrates and Araldite 2031 adhesive. To quantify this edge effect, a specific coefficient, named coefficient of stress concentration was defined: it is the ratio of the maximum shear stress to the average shear stress. This coefficient helps to calculate maximum strength of the joint since experimentally, only average shear stress could be measured. A numerical analysis at the midplane of the joint was carried out to investigate the effect of geometrical and material parameters on this stress concentration factor. It was found that this factor is constant with the time once the equilibrium is established. Moreover, this stress concentration coefficient decreases with higher Young's modulus of the adherents, lower Young's modulus of the adhesive, thicker and shorter adhesive layer. A unified parameter involving geometrical and mechanical parameters of the specimen was established to quantify this stress concentration factor.

This paper deals with the experimental characterization of a bulk adhesive fracture in the quasi-static range using a conventional machine and at high strain rates using the Hopkinson bar technique. For very high strain rates, the direct impact Hopkinson bar technique is used. The studied adhesive is a toughened epoxy which can be used for impact resistance in bonded assemblies. It is worth studying the adhesive sensitivity to strain rate as a bulk material in order to distinguish between its response within a structure when used to bond substrates and its response as pure material. Experiments were carried out under compression and shear loadings. A special grip was conceived to mount the specimen for shear tests. In both loading types, this adhesive was found to be highly strain-rate-sensitive. The adhesive strength increases with strain rate until reaching a maximum value then it drops for very high strain rates. Although this behavior is uncommon, it has been reported already in three previous works.

The influence of nonsymmetric rotation of laminates on the shear and peel stresses in the adhesive layer of adhesively bonded double-lap composite joints (DLJ) subjected to in-plane impact compressive loadings is investigated by using a three-dimensional finite-element analysis. The compressive in-plane impact on DLJ is simulated using the direct Hopkinson bar system, and the specimen is impacted by an incident bar. It is found that the rotation of any adherend from the 0° orientation leads to a decrease in the average shear stress in the adhesive layer, but the maximum peel stress is affected only by the longitudinal stiffness of the outer adherend and decreases when this stiffness diminishes.

The monomer, 4-acrylamidobenzenesulfonamide (ABS), was synthesized via reaction of acryloyl chloride with 4-aminobenzenesulfonamide in acetone at 0 °C. This monomer was then grafted onto chitosan using solution containing 2% acetic acid and mixture of K2S2O8 and Na2SO3 as the redox promoter. An optimal G% of 150% was obtained when the process is conducted at 60 °C for 3 h employing 3.0 × 10−3 M K2S2O8 and 1.5 × 10−3 M Na2SO3. The graft copolymers, chitosan-g-poly(4-acrylamidobenzenesulfonamide), were characterized by using FTIR, XRD, and SEM. The results were shown that the crystallinity of chitosan is enhanced by increasing the monomer content through the grafting process. Potential Antimicrobial activities of the permethyl ammonium salt forms of chitosan and its grafted copolymers against selected microorganisms were evaluated. The results show that the graft copolymers display better inhibitory effects on the growth of bacteria and some fungi than does chitosan.

N-Acryloyl morpholine, NAM, was grafted onto chitosan utilizing homogeneous conditions with 1% acetic acid as the solvent, and potassium persulfate and sodium sulfite as the redox initiator. The effects of various reaction parameters, such as time, temperature, and monomer and initiator concentrations, on the percentage of grafting (G%) and the grafting efficiency (E%) were determined. The results show that an optimal G% of 112% is obtained when the process is conducted at 65 °C for 4 h employing a 1:0.25 ratio of K2S2O8 and Na2SO3 at a concentration of 3.0 × 10−3 M. The progress and extent of the grafting process were monitored by using elemental analysis, FTIR, and 1H NMR spectroscopy. The graft copolymer showed a remarkably improved crystallinity, as compared to the unmodified chitosan, based on the FESEM, XRD, and DSC results. Chitosan-g-poly(N-acryloyl morpholine) (Cs-PNAM), the copolymer obtained by using this procedure, was characterized by utilizing FTIR, FESEM, TGA, and XRD analysis. A plausible mechanism for the grafting reaction has been suggested. As expected, the results of an evaluation of antibacterial and antifungal activities show that the grafted chitosan copolymers exhibit stronger inhibitory effects against both types of microbes than does chitosan. Moreover, the size of the inhibition zone created by the graft copolymer was observed to be proportional to its G% corresponding to its morpholine content. The extent and pH dependence of uptake of different types of dyes (acidic: EBT, and MV; and basic: MB) by grafted chitosan in pH 6.5 aqueous solutions was determined. The results show that, in comparison to chitosan, grafted chitosan exhibits greater absorption of the acid dyes and that the extent of absorption increases with decreasing temperatures.

A novel method has been developed to modify the natural polymer chitosan. The process utilizes a monomer prepared by employing a Morita–Baylis–Hillman (MBH) reaction. Specifically, the vinyl monomer 2-[hydroxy(pyridin-3-yl)methyl]acrylonitrile (HPA) was synthesized using a high-yielding MBH reaction of acrylonitrile with pyridine-3-carboxaldehyde in the presence of 1,4-diazabicyclo[2.2.2]octane. Conversion of HPA to 2-cyano-1-(pyridin-3-yl)allyl acrylate (CPA) was then carried out by reaction of acryloyl chloride. The highly functionalized monomer CPA was grafted onto chitosan through a reaction in 2% acetic acid containing a persulfate and a sulfite (K2S2O8/Na2SO3) as redox promoter. An optimal grafting percentage of 123% is obtained when the grafting process is conducted at 60 °C for 4 h employing a 1:0.5 ratio of K2S2O8 and Na2SO3 at a concentration of 2.5 × 10−3 mol L−1. Chitosan-graft-poly[2-cyano-1-(pyridin-3-yl)allyl acrylate] graft copolymers, having various grafting percentages, were characterized using Fourier transform infrared, 1H NMR and 13C NMR spectroscopies, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. Finally, the results of studies probing the antimicrobial activities of the polymers against selected microorganisms show that the graft copolymers display higher growth inhibition activities against bacteria and fungi than does chitosan. © 2014 Society of Chemical Industry

Graft copolymerization of the novel monomer 2-(furan-2-carbonyl) acrylonitrile (FCAN) onto chitosan was carried out under heterogeneous conditions using potassium persulfate and sodium sulfite as a redox system. The monomer, FCAN, was synthesized by iodoxybenzoic acid promoted oxidation of 2-(furan-2-yl(hydroxyl)methyl)acrylonitrile FHMAN, which was prepared by using a Baylis Hillman reaction between acrylonitrile and furfural. The graft copolymers were characterized by using FTIR, 1H NMR, 13C NMR spectroscopy, along with XRD, TGA, SEM. The effects of various parameters on the grafting percentage (G%) and the efficiency of grafting (E%) were determined. The results show that an optimal grafting percentage of 145% results when the process is conducted at 55 °C for 3.5 h employing a 1:0.5 ratio of K2S2O8 and Na2SO3. The grafted copolymers with varying grafting percentages were found to display a marked increase in swelling in water, as compared to chitosan, and swelling was observed to increase as the acidity of the medium increases. The antifungal and antibacterial activites of chitosan and the grafted copolymers against selected micro-organisms (bacteria; Bacillus subtilis, Escherichia coli and fungi; Aspergillus niger, Penicillium digitatum, Staphylococcus aureus) were determined. The results show that growth inhibition by the copolymers is in the following order: E. Coli > Bacillus > S. Aureus > Aspragillus > Pennicilium, reflective of a higher activity against bacteria than fungi. In addition, a general trend was observed in which increases in biological activities are directly dependent on grafting percentages, presumably a consequence of the presence of more furan moieties in the polymer backbone.

Chitosan-grafted-poly(4-vinylpyridine) (Cs-PVP) copolymers could be synthesized under heterogeneous conditions in presence of a potassium persulfate and sodium sulfite redox system. The synthesized graft copolymer could be utilized effectively, in the form of beads, as an efficient catalyst for Michael additions of active methylenes to functionally substituted alkenes. Moreover, methyl moiety oxidation in methyl pyridazinyl carbonitriles by H2O2 in the presence of chitosan-g-polyvinyl pyridine–supported iron (III) complex, Cs-PVP/Fe, could be affected. A variety of pyrans, naphthopyrans, and thiopyrans could be synthesized efficiently in the presence of these graft copolymer beads by novel catalytic routes. These polymeric catalysts could be used instead of the old toxic commercial organic basic catalysts, piperidine or pyridine, and could be readily isolated from the reaction mixture and recycled several times without significant loss of catalytic activity.

In the present study, a novel series of 2-(2-(3-aryl-5-substituted-1,3,4-thiadiazol-2(3H)-ylidene)hydrazinyl)-4,4-diphenyl-1H-imidazol-5(4H)-one derivatives were designed and prepared via the reaction of the most versatile, hitherto unreported 2-(5-oxo-4,4-diphenyl-4,5-dihydro-1H-imidazol-2-yl)-N-phenylhydrazinecarbothioamide with the appropriate hydrazonoyl halides. In addition, some thiazole derivatives were prepared. The structures of the newly synthesized compounds were established based on spectroscopic evidences and their alternative syntheses. Some of the newly synthesized compounds have been evaluated for their anticancer activity against a liver carcinoma cell line HEPG2-1. Moreover, their structure-activity relationship (SAR) was explored for further development in this area. The results indicated that many of the tested compounds showed moderate to high anticancer activity with respective to doxorubicin as a reference drug. Consequently, the new synthesized series of thiadiazole-imidazole derivatives are considered as powerful anticancer agents.