Electrically conductive epoxy‐based nanocomposite adhesives loaded with silver‐coated copper and silver‐coated reduced graphene oxide nanoparticles

In this research, a conductive adhesive based on epoxy resin as the polymer matrix and silver‐coated copper powder and silver‐coated reduced graphene oxide as conductive fillers was synthesized. Graphene oxide was synthesized by modified Hummer's method. It was reduced and modified by silver powder. Copper particles were coated with silver using the electroless plating method. Finally, conductive nanocomposite adhesives were prepared using conductive fillers with different weight fractions. The structural properties of fillers were identified by Fourier‐transform infrared (FTIR) and induced coupled plasma (ICP) analysis and the morphology of the samples by scanning electron microscopy (SEM). Finally, conductive properties, lap shear strength, and thermal stability of adhesive were evaluated. The conductive adhesive prepared with optimized properties have 70% weight percentage silver‐coated copper powder and 1% weight percentage silver‐coated reduced graphene oxide. The bulk resistivity of the optimum sample was 1.6 × 10^‐2 Ω.cm, and the lap shear strength was 7.10 MPa. Also, thermogravimetric analysis showed that the weight loss of adhesive decreased from 88.72% to 30.55% during heating, which showed the addition of fillers improves the thermal stability of adhesive.     

A 3-D bonding perspective of the factors influencing the relative stability of the S1/S0 conical intersections of the penta-2,4-dieniminium cation (PSB3)

A balanced treatment of the covalent and ionic contributions to the ground and excited states originating from torsion about double bonds is known to be strongly dependent on the presence of dynamic electron correlation. We undertake an analysis of the minimum energy pathways corresponding to deactivation of the first excited singlet state of PSB3. In doing so we consider torsion about the three double bonds including other intramolecular degrees of freedom, such as the bond length alternation. The 3-D bond-path analysis provides a new ‘bond-localized orbital-like’ directional interpretation of bonding. Therefore, we present a more sophisticated method of determination of the degree of covalent and ionic contributions known to be responsible for altering the relative stability of the S₁/S₀ conical intersections. The results presented suggest that the commonly used simplified multi-reference methodologies that often result in incorrect predictions for the excited state deactivation reaction mechanism.     

Molecular engineering of the electronic,structural, and electrochemical properties of nanostructured 1-methyl-4-phenyl 1,2,4 triazolium-based [PhMTZ][X<Subscript>1–10</Subscript>] ionic liquids through anionic changing

In the present work, molecular engineering of the physicochemical characteristics of ion pairing in 1-methyl-4-phenyl 1,2,4 triazolium-based ionic liquids [PhMTZ][X] (X_1–10 = CH₃CO₂ ^?, Cl^?, NO₃ ^?, CF₃CO₂ ^?, BF₄ ^?, ClO₄ ^?, N(CN)₂ ^?, PF₆ ^?, NTf₂ ^?, and C(CN)₃ ^?) are explored using at M06-2X/6–311++G(d,p) level. The binding Gibbs free energy of ion pairs are reevaluated using ab initio MP2 method and dispersion corrected M06-2X-D3, B2PLYP, B2PLYP-D, and mPW2PLYP-D functionals. Comparison of Gibbs free bottom electrodes (BEs) calculated by B2PLYP and B2PLYP-D functionals reveals that the contribution of dispersion energy to the total BEs vary from 9% for X1 to 17% for X = 10. Besides, the range of the dispersion contribution estimated by M06-2X-D3 functional is found to be 0.6% for X₂ to 5% for X₃. The Gibbs free BEs in solvent media, Gibbs free energy and enthalpy of formation, electrochemical windows, anodic and cathodic stability, volumetric and electron density properties, charge transfer values, and electrostatic maps are evaluated.     

Processing and Properties of Nanocomposite Filament Yarns with Various Filler Concentrations from Two Different Modification Methods

In this research, the possibility of producing and processing nanocomposite polypropylene filament yarns with permanent antimicrobial efficiency has been assessed by comparing two different methods. Therefore two approaches were used to mix various blending contents of antimicrobial agents based on silver/TiO₂ nano particles with PP: 1) mixing of PP powder and inorganic nanocomposite powder as an antibacterial agent with the appropriate concentration in a twin screw extruder, preparing modified granules and feeding them to the melt spinning machine, 2) producing masterbatch by a twin screw extruder and blending it with PP in the melt spinning process. In both methods, pure PP and all other combined samples had an acceptable spinnability at the spinning temperature of 240 °C and take-up speed of 2000 m/min. After producing as-spun filament yarns by a pilot plant melt spinning machine, samples were drawn, textured and finally weft knitted. Physical and structural properties of as-spun and drawn yarns with constant and variable draw ratios were investigated and compared. Moreover, the DSC, SEM and FTIR techniques have been used for samples characterization. Finally antibacterial efficiency of knitted samples was evaluated. The experimental results indicated that the maximum crystallinity reduction of modified as-spun yarns reached 5%. But by applying method 2 (masterbatch), crystallinity of modified as-spun yarns remained unchanged compared to pure yarn. However, drawing procedure has compensated this difference. By applying the second method, the drawing generally improved the increase of tenacity and modulus of modified fibers, whereas in method 1 the opposite effect was noticed in the case of constant draw ratio. Although the biostatic efficiency of nanocomposite fibers was excellent in both methods, modified fabrics obtained from method 1 showed higher bioactivity.     

Complementary short syntheses of (±)-methyl shikimate

Two syntheses of (±)-methyl shikimate from the adduct of furan and methyl acrylate are described. One requires the regioselective hydroxylation of (±)-5β,6β-dihydroxy-$\text{O}$,$\text{O}$-isopropylidene-2-methoxycarbonylcyclohexa-1,3-diene and the other $\text{cis}$-dihydroxylation of (±)-5-hydroxy-1-methoxycarbonylcyclohexa-1,3-diene.     

Isocyanide-based four-component synthesis of 1,3-indandionylamidinium betaines

An efficient approach for the synthesis of novel 1,3-indandionylamidinium betaines via four-component reaction of 1,3-indandione, aldehydes, amines, and isocyanides, without assistance of any catalyst and under mild reaction conditions has been reported. The structures of these compounds were confirmed by IR, mass spectroscopic, ¹H NMR, ¹³C NMR, and single-crystal X-ray diffraction studies.     

Synthesis,characterization, thermal,electrochemical, and DFT studies of mononuclear cyclopalladated complexes containing bidentate phosphine ligands and their biological evaluation as antioxidant and antibacterial agents

The non-symmetric phosphorus ylides and their Pd(II) complexes have been synthesized as potential antioxidant and antibacterial compounds and their structures were elucidated using a variety of physicochemical techniques. The reaction of 1 equiv non-symmetric phosphorus ylides, Ph₂PCH₂PPh₂C(H)C(O)PhX (X = Br (Y¹), Cl (Y²), NO₂ (Y³), OCH₃ (Y⁴)) with [Pd(dppe)Cl₂] (M¹), followed by treatment with 2 equiv AgOTf led to monomeric chelate complexes, [(dppe)Pd(Ph₂PCH₂PPh₂C(H)C(O)PhX)] (OSO₂CF₃)₂ (X = Br (C¹), Cl (C²), NO₂ (C³), OCH₃ (C⁴)), which contain a five-membered P,P chelate ring in one side and a five-membered P,C chelate ring in the other side. Palladium ion complexes were synthesized and investigated by cyclic voltammetry, FT-IR, UV–visible, multinuclear (¹H, ³¹P and ¹⁹F) NMR, thermal analysis and ESI-mass spectroscopic studies. Some complexes and ligands have been studied by powder XRD and single crystal X-ray diffraction techniques. FT-IR and ³¹P NMR studies revealed that the ylides Y are coordinated to the metal ions via the terminal phosphorus (P_c) of the ylides and methene group (CH). The proposed coordination geometry around the Pd atom in these complexes is defined as slightly distorted square planar by UV-Visible and DFT studies. Thermal stability of all complexes was also shown by TG/DTG methods. Furthermore, the electrochemical behavior of the complexes was investigated by cyclic voltammetry. The results indicate that all complexes are successfully synthesized from the initial ligands. All complexes were analyzed for their antioxidant properties by DPPH free radical scavenging assay. In addition, the antibacterial effects of the hexane-solved complexes were investigated by disc diffusion method against four Gram positive and negative bacteria. All complexes represented antibacterial activity against bacteria tested especially on Gram positive ones. A theoretical study on the structure, ¹H and ³¹P NMR chemical shifts and the interaction energy between the Pd²⁺ ion and ligands dppe and ylide Y is also reported.     

Plant-Based Gums and Mucilages Applications in Pharmacology and Nanomedicine: A Review

Gums are carbohydrate biomolecules that have the potential to bind water and form gels. Gums are regularly linked with proteins and minerals in their construction. Gums have several forms, such as mucilage gums, seed gums, exudate gums, etc. Plant gums are one of the most important gums because of their bioavailability. Plant-derived gums have been used by humans since ancient times for numerous applications. The main features that make them appropriate for use in different applications are high stabilization, viscosity, adhesive property, emulsification action, and surface-active activity. In many pharmaceutical formulations, plant-based gums and mucilages are the key ingredients due to their bioavailability, widespread accessibility, non-toxicity, and reasonable prices. These compete with many polymeric materials for use as different pharmaceuticals in today’s time and have created a significant achievement from being an excipient to innovative drug carriers. In particular, scientists and pharmacy industries around the world have been drawn to uncover the secret potential of plant-based gums and mucilages through a deeper understanding of their physicochemical characteristics and the development of safety profile information. This innovative unique class of drug products, useful in advanced drug delivery applications, gene therapy, and biosynthesis, has been developed by modification of plant-based gums and mucilages. In this review, both fundamental and novel medicinal aspects of plant-based gums and mucilages, along with their capacity for pharmacology and nanomedicine, were demonstrated.     

Effect of multi-ethers and conventional alkoxysilanes as external donors on the 4th generation Ziegler-Natta catalysts for propylene polymerization

The multi-ether compounds with different numbers of methoxy groups containing 1,3-dimethoxy-2,2-bis(methoxymethyl)propane and 1-methoxy-2,2-bis(methoxymethyl)butane were synthesized using the Williamson reaction from pentaerythritol and 1,1,1-tris(hydroxymethyl)propane, respectively, in the presence of sodium hydride and methyl iodide in tetrahydrofuran and they were characterized by ¹H NMR, ¹³C NMR, and FTIR spectroscopy. These compounds were employed as external donors in the polymerization of propylene using the industrial Ziegler-Natta catalyst. A commercial spherical MgCl₂-supported Ziegler-Natta catalyst containing diisobutyl phthalate as the internal donor was used for the polymerization of propylene. The role of ether compounds and industrial alkoxysilanes on the properties of polypropylene were studied using the xylene solubility method, melt flow index, gel permeation chromatography, scanning electron microscopy, and differential scanning calorimetry. The addition of the electron donors has led to improvements in the activity and selectivity of the Ziegler-Natta catalyst system.     

Synthesis and MRSA PK inhibitory activity of thiazole containing deoxytopsentin analogues

The public health care crisis caused by the emergence of drug resistant bacterial strains, e.g., methicillin resistant Staphylococcus aureus (MRSA) has underlined the urgent need to accelerate the discovery of new chemical entities active against antibiotic resistant bacteria. We report here the synthesis of a series thiazole containing deoxytopsentin analogues, which show moderate activity against a target MRSA pyruvate kinase enzyme: an evolutionary conserved hub protein critical for bacterial survival. A Hantzsch thiazole coupling between α-oxo-1H-indole-3-thioacetamides and 2-bromo-1-(1H-indol-3-yl)-ethanones provided facile access to the thiazole containing deoxytopsentin compounds.