Direct transformation of coumarins into orange-red emitting rhodols

The lactone carbonyl group of coumarin derivatives has been shown to participate in intramolecular Knoevenagel condensations, enabling the unprecedented direct transformation of coumarins into rhodols. The resulting rhodols, possessing two...

Recycling and valorization of LDPE: direct transformation into highly ordered doped-carbons and its application as electro-catalyst for the oxygen reduction reaction

The energy demand and the environmental situation make necessary the development of advanced catalysts for energy applications. Considering the large volumes of plastic waste, the transformation of organic polymers into...

Coherent interfaces with mixed hybridization govern direct transformation from graphite to diamond

Understanding the direct transformation from graphite to diamond has been a long-standing challenge with great scientific and practical importance. Previously proposed transformation mechanisms1-3, based on traditional experimental observations that lacked atomistic resolution, cannot account for the complex nanostructures occurring at graphite-diamond interfaces during the transformation4,5. Here, we report the identification of coherent graphite-diamond interfaces constituted with four structural motifs in partially transformed graphite samples recovered from static compression, using high-angle annular dark-field scanning transmission electron microscope. These observations provide vital insight into possible pathways of the transformation. Theoretical calculations confirm that transformation through these coherent interfaces is energetically favored to those through other paths previously proposed1-3. The graphite-to-diamond transformation is governed by the formation of nanoscale coherent interfaces (diamond nucleation), which, under static compression, advance to consume the remaining graphite (diamond growth). These results also shed light on transformation mechanisms of other carbon materials and boron nitride under different synthetic conditions.

Sustainable polyesters via direct functionalization of lignocellulosic sugars

The development of sustainable plastics from abundant renewable feedstocks has been limited by the complexity and efficiency of their production as well as their lack of competitive material properties. Here, we demonstrate the direct transformation of the hemicellulosic fraction of non-edible biomass into a diester plastic precursor at 83% yield (95% from commercial xylose) during integrated plant fractionation with glyoxylic acid. Melt polycondensation of the resulting xylose-based diester with a range of aliphatic diols led to high-molecular weight amorphous polyesters with combined high glass transition temperatures, tough mechanical properties, and strong gas barriers, which could be processed by injection-molding, thermoforming, and 3D-printing. These polyesters could then be chemically recycled from mixed plastic waste streams or digested under biologically relevant conditions. The transformation’s simplicity led to projected costs that were competitive with fossil alternatives and significantly reduced associated greenhouse gas emissions, especially if glyoxylic acid was sourced from CO2.

Redox-enabled direct stereoconvergent heteroarylation of simple alcohols

The direct transformation of racemic feedstock materials to valuable enantiopure compounds is of significant importance for sustainable chemical synthesis. Toward this goal, the radical mechanism has proven uniquely effective in stereoconvergent carbon-carbon bond forming reactions. Here we report a mechanistically distinct redox-enabled strategy for an efficient enantioconvergent coupling of pyrroles with simple racemic secondary alcohols. In such processes, chirality is removed from the substrate via dehydrogenation and reinstalled in the catalytic reduction of a key stabilized cationic intermediate. This strategy provides significant advantage of utilizing simple pyrroles to react with feedstock alcohols without the need for leaving group incorporation. This overall redox-neutral transformation is also highly economical with no additional reagent nor waste generation other than water. In our studies, oxime-derived iridacycle complexes are introduced, which cooperate with a chiral phosphoric acid to enable heteroarylation of alcohols, accessing a wide range of valuable substituted pyrroles in high yield and enantioselectivity.

Актуатор с последовательным соединением стержня из сплава с памятью формы и упругого элемента смещения

One of the most promising applications of shape memory alloys (SMA) is their use for creating working bodies of power exciters (actuators). The working body of the actuator must perform certain movements due to shape memory phenomena (heating, working stroke of the actuator) and the accumulation of direct transformation deformations (cooling, idling of the actuator). It is known that the process of deformation of SMA during cooling occurs only in the presence of mechanical action, while the return to the original form during heating occurs in the absence of a corresponding mechanical action and even in the presence of a sufficiently large counteraction. To ensure the possibility of not only working, but also idling of the actuator, the working body of the SMA is connected to the elastic bias element so that both of these elements are deformed together. In this case, when the SMA element is heated, it is deformed due to the shape memory phenomenon, which leads to the deformation of the bias element associated with the working body and the appearance, both in this element and in the working body, of mechanical stresses that increase with the temperature of the SMA element. It is these stresses, which continue to act during the cooling of the working body, that ensure its deformation in the opposite direction at the stage of cooling of the working body and the corresponding direct transformation into SMA. In this paper, the behavior of an actuator consisting of a SMA rod and an elastic rod (an bias element) connected in series, the total length of which is assumed to be unchanged, is analytically investigated. The influence of the system parameters on the stresses in the SMA rod and the value of the working stroke of the actuator is investigated. The conditions for the implementation of the closed two way shape memory effect in this system are determined.

CARBON-LIKE UNITS FOR A NANOSIZED TOOL BASED ON THE USE OF BORON NITRIDE AND DIAMOND

Phase transformations of pyrolytic boron nitride were studied under thermobaric conditions, providing direct transformation of a hexagonal structure into a cubic one. If only the martensitic mechanism of the cooperative rearrangement of atoms is realized, diamond-like aggregates with an equiaxed highly dispersed structure and submicron grain sizes are formed. The presence of a solvent-catalyst (RC) in the system leads to an increase in the particle size of the cubic phase due to recrystallization by the diffusion mechanism, and the high catalytic activity of RC causes the appearance of zones of directional crystal growth in the synthesized samples.