Effect of layered hydroxide salts,produced by two different methods,on the mechanical and thermal properties of poly(methyl methacrylate)

In this study, eight different layered hydroxide salts (LHSs) based on copper and zinc, intercalated with stearate, myristate, azelate, and poly(ethylene glycol) (PEG) monolaurate, were prepared. All the LHSs were produced according two different methods: co‐precipitation (direct method) and synthesis of zinc hydroxide nitrate (ZHN) and copper hydroxide nitrate (CHN) followed by exchange reaction (indirect method). The synthetic layered compounds were characterized by X‐ray diffraction (XRD) and thermogravimetric analysis (TGA). TGA results revealed that higher thermal stability was observed for the LHSs synthesized by direct method. The effects of all these LHSs on the thermal and mechanical properties of poly(methyl methacrylate) (PMMA) nanocomposites were investigated. The LHSs percentage (wt%) in the PMMA was fixed at 1%. PMMA and PMMA nanocomposites were produced by in situ bulk polymerization. Compared to PMMA, all the nanocomposites exhibited higher thermal stability. The nanocomposite containing ZHN(stearate) by indirect method revealed both T₅₀ (temperature at which a 50% loss of mass occurs) and T₉₀ (temperature at which a 90% loss of mass occurs) 71°C higher than PMMA. Compared to PMMA, the nanocomposite with ZHN(PEG monolaurate) exhibited an increase of 14% in the elastic modulus, at 30°C. POLYM. ENG. SCI., 59:1065–1074, 2019. © 2019 Society of Plastics Engineers     

Seedless Cu Electroplating on Ru-W Thin Films for Metallisation of Advanced Interconnects

For decades, Ta/TaN has been the industry standard for a diffusion barrier against Cu in interconnect metallisation. The continuous miniaturisation of transistors and interconnects into the nanoscale are pushing conventional materials to their physical limits and creating the need to replace them. Binary metallic systems, such as Ru-W, have attracted considerable attention as possible replacements due to a combination of electrical and diffusion barrier properties and the capability of direct Cu electroplating. The process of Cu electrodeposition on Ru-W is of fundamental importance in order to create thin, continuous, and adherent films for advanced interconnect metallisation. This work investigates the effects of the current density and application method on the electro-crystallisation behaviour of Cu. The film structure, morphology, and chemical composition were assessed by digital microscopy, atomic force microscopy, scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The results show that it was possible to form a thin Cu film on Ru-W with interfacial continuity for current densities higher than 5 mA·cm⁻²; however, the substrate regions around large Cu particles remained uncovered. Pulse-reverse current application appears to be more beneficial than direct current as it decreased the average Cu particle size.     

Thermal dehydration of Y(TFA)3(H2O)3: Synthesis and molecular structures of [Y(μ,η1:η1-TFA)3(THF)(H2O)]1∞ · THF and [Y4(μ3-OH)4(μ,η1:η1-TFA)6(η1-TFA)(η2-TFA)(THF)3(DMSO)(H2O)] · 6THF (TFA = trifluoroacetate)

In order to obtain a better anhydrous precursor for various applications in materials science and catalysis, thermal dehydration reactions of Y(TFA)₃(H₂O)₃ (TFA = trifluoroacetate) (A) were investigated. Thermal treatment of A at different temperatures under vacuum (5 × 10^?2 mm) for several hours failed to give totally anhydrous yttrium trifluoroacetate (as indicated by IR). Two different complexes, a partially dehydrated [Y(μ,η¹:η¹-TFA)₃(THF)(H₂O)]_1∞·THF (1) and a partially hydrolyzed [Y₄(μ₃-OH)₄(μ,η¹:η¹-TFA)₆(η¹-TFA)(η²-TFA)(THF)₃(DMSO)(H₂O)] · 6THF (2), were obtained with good and moderate yield, respectively, by crystallization of two different thermally treated batches of A from THF (or THF + DMSO) at room temperature. More efficient dehydration of A could be achieved at 200 °C in a furnace, the obtained anhydrous yttrium tris-trifluoroacetate giving Y(TFA)₃(THF)₂ (3) on crystallization from THF. All the products were characterized by elemental analyses, FT-IR and ¹H NMR spectroscopy as well as thermo-gravimetric analysis. In addition, single crystal X-ray structures are reported for 1 and 2, which show either a terminal (η¹ and η²) or bridging (μ,η¹:η¹) bonding behavior of the TFA ligand.     

Cladosporin Derivatives Obtained by Biotransformation Provide Guidance for the Focused Derivatization of this Antimalarial Lead Compound

Cladosporin, a natural product known for decades, has recently been discovered to display potent and selective antiplasmodial activity by inhibition of lysyl-tRNA synthetase. It was subjected to a panel of oxidative biotransformations with one fungal and two actinomycetes strains, as well as a triple mutant bacterial CYP102A1, yielding eight, mostly hydroxylated, derivatives. These new compounds covered a wide chemical space and contained two pairs of epimers in the tetrahydropyran ring. Although less potent than the parent compound, all analogues showed activity in a cell-based synthetase assay, thus demonstrating uptake and on-target activity in living cells with varying degrees of selectivity for the enzyme lysyl-tRNA synthetase from Plasmodium falciparum and highlighting sites suitable for synthesis of future cladosporin analogues. Compounds with adjacent hydroxy functions showed different MS/MS fragmentation that can be explained in terms of an, in some cases, regioselective loss of water followed by a retro-Diels–Alder reaction.     

Polystyrene/kaolinite nanocomposite synthesis and characterization via in situ emulsion polymerization

Polymer Bulletin - The polymer nanocomposites polystyrene (PS)/kaolinite (Kao) were synthesized by in situ emulsion polymerization. First Kao was modified using dimethylsulfoxide (DMSO) by a...     

Recent advances in the development of supported carbon membranes for gas separation

Carbon membranes have emerged in the 70's and have been presenting promising results for application in processes involving gas separation because of their sieving effects. The carbon membranes are obtained by pyrolysis of a precursor polymer beyond its initial decomposition temperature under essentially inert conditions. Supported and unsupported carbon membranes can be produced, but the former are distinguished for the industrial separation of gases due to the improved mechanical strength and high chemical and thermal stability. In this context, different types of support, coating methods and pyrolysis conditions for supported carbon membranes have been reported in the literature, in order to improve the separation capability of gas mixtures in respect to permeability and selectivity. The aim of this review article is to report and discuss the evolution of supported carbon membrane in the last 10 years in respect to configuration, transport mechanisms, manufacturing processes and its main applications, highlighting the main challenges still to be overcome for this technology to be applied industrially.     

Redox‐Driven Host–Guest Interactions Allow the Controlled Release of Captured Cells on RGD‐Functionalized Surfaces

A quartz crystal microbalance technique with dissipation monitoring and a complementary optical microscopy technique were used for monitoring the capture and release of specific cells on a surface displaying a bifunctional molecular device, composed of a molecular scaffold endowed with the cell recognition property of an RGD ligand and a β‐CD/Fc redox‐switchable system.