The chemistry of N-heterocyclic carbenes (NHCs) has witnessed tremendous development in the past two decades: NHCs have not only become versatile ligands for transition metals, but have also emerged as powerful organic catalysts in molecular chemistry and, more recently, in metal-free polymer synthesis. To understand the success of NHCs, this review first presents the electronic properties of NHCs, their main synthetic methods, their handling, and their reactivity. Their ability to activate key functional groups (e.g. aldehydes, esters, heterocycles, silyl ketene acetals, alcohols) is then discussed in the context of molecular chemistry. Focus has been placed on the activation of substrates finding analogies with monomers (e.g. bis-aldehydes, multi-isocyanates, cyclic esters, epoxides, N-carboxyanhydrides, etc.) and/or initiators (e.g. hydroxy- or trimethylsilyl-containing reagents) employed in such “organopolymerisation” reactions utilizing NHCs. A variety of metal-free polymers, including aliphatic polyesters and polyethers, poly(α-peptoid)s, poly(meth)acrylates, polyurethanes, or polysiloxanes can be obtained in this way. The last section covers the use of NHCs as structural components of the polymer chain. Indeed, NHC-based photoinitiators, chain transfer agents or functionalizing agents, as well as bifunctional NHC monomer substrates, can also serve for metal-free polymer synthesis.

N-Heterocyclic carbenes (NHCs) as organocatalysts and structural components in metal-free polymer synthesis

This manuscript reports on the recent progress and the remaining materials challenges in the development of coated conductors (CCs) for power applications and magnets, with a particular emphasis on the different initiatives being active at present in Europe. We first summarize the scientific and technological scope where CCs have been raised as a complex technology product and then we show that there exists still much room for performance improvement. The objectives and CC architectures being explored in the scope of the European project EUROTAPES are widely described and their potential in generating novel breakthroughs emphasized. The overall goal of this project is to create synergy among academic and industrial partners to go well beyond the state of the art in several scientific issues related to CCs’ enhanced performances and to develop nanoengineered CCs with reduced costs, using high throughput manufacturing processes which incorporate quality control tools and so lead to higher yields. Three general application targets are considered which will require different conductor architectures and performances and so the strategy is to combine vacuum and chemical solution deposition approaches to achieve the targeted goals. A few examples of such approaches are described related to defining new conductor architectures and shapes, as well as vortex pinning enhancement through novel paths towards nanostructure generation. Particular emphasis is made on solution chemistry approaches. We also describe the efforts being made in transforming the CCs into assembled conductors and cables which achieve appealing mechanical and electromagnetic performances for power systems. Finally, we briefly mention some outstanding superconducting power application projects being active at present, in Europe and worldwide, to exemplify the strong advances in reaching the demands to integrate them in a new electrical engineering paradigm.

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Coated conductors for power applications: materials challenges

https://hal.archives-ouvertes.fr/hal-01366512/document

Update and challenges in organo-mediated polymerization reactions

Techniques are reported for sputter deposition of biaxially oriented buffer-layers on textured Ni tapes. These buffered tapes can be employed as long, flexible, or large area substrates for biaxially-aligned high-temperature superconductors (HTS) with high critical current density Jc. Using deposition techniques at temperatures as low as 25°C, epitaxial Pd or Pt films were first deposited as a base layer on the textured Ni tapes, followed by deposition of biaxially oriented Ag or CeO2 buffer layers. Using Ar/4%H2 sputter gas, biaxially oriented CeO2 films were also grown directly on the textured Ni tapes, followed by the epitaxial growth of YSZ films. All the films show both strong in-plane and out-of-plane orientations. The effects of Ni surface smoothness on buffer-layer texture were also investigated.

Deposition of biaxially-oriented metal and oxide buffer-layer films on textured Ni tapes: New substrates for high-current, high-temperature superconductors

Organic electrosynthesis is an enabling and sustainable technology, which constitutes a rapidly expanding field of research. Electrochemical approaches serve as convenient and green alternatives to ...

Organic Electrosynthesis: Applications in Complex Molecule Synthesis

Chitosan functionalization of titanium and Ti6Al4V alloy with chloroacetic acid as linker agent.

On the use of surfactants in the electrochemical preparation of porous silicon

An electrochemical alternative strategy to the synthesis of β-lactams

Polarity reversal induced by electrochemically generated thiazol-2-ylidenes: The Stetter reaction

Preliminary results concerning the fabrication and use of manganese oxide thin film electrodes are presented. Different deposition techniques were employed and compared in order to obtain enhanced anodic oxidation of organic pollutants. In particular, manganese oxide films were produced by cathodic electrodeposition from aqueous KMnO4 solutions (Type-A), by anodic electrodeposition from aqueous MnSO4 solutions (Type-B) and by thermal decomposition from alcoholic solutions (Type-C). All the films were grown on titanium foil covered with a thermally deposited ruthenium oxide inter-layer to ensure good electrical contact. In addiction to characterization by cyclic voltammetry (CV), X-Ray diffraction (XRD), and profilometric measurements, the electrodes were tested for the treatment of aqueous solutions containing the azo dye Reactive Violet 5 (RV5), as a model organic pollutant. The azo-dye degradation, conducted under galvanostatic conditions in an undivided reactor, was evaluated by UV–Vis measurements and COD analysis. In the presence of small concentration of NaCl, all electrodes exhibited good decolorization and COD reduction capability. The type-B electrodes showed the best performances. The Type-C electrodes accounted for anodes less performant with negligible formation of active chlorine.

Giovanni Sotgiu

Papers

Chitosan functionalization of titanium and Ti6Al4V alloy with chloroacetic acid as linker agent.

On the use of surfactants in the electrochemical preparation of porous silicon

An electrochemical alternative strategy to the synthesis of β-lactams

Polarity reversal induced by electrochemically generated thiazol-2-ylidenes: The Stetter reaction

Production and Characterization of Manganese Oxide- Based Electrodes for Anodic Oxidation of Organic Compounds