A synthetic method for the transformation of polyimides into poly(ionic liquid)s with improved properties is suggested.
Carbon dioxide (CO2) levels are continuously growing, and CO2 is believed to be a significant contributor to global warming and climate change. Therefore, there is a great interest in the development of highly efficient technologies to curb CO2 emissions of current energy sources. In this context to combat such issues, poly(ionic liquid)s (PILs) offer an extremely versatile and tunable platform to fabricate a wide variety of sorbents for CO2 capture. To date, the majority of poly(ionic liquid)s studied for CO2 capture is related to carbochain polymers (acrylate and styrene polyelectrolytes), while it is generally accepted that polymers with more basic backbones such as amides, urethanes or amidoxines can considerably enhance the CO2 absorption capacity. Thus, a series of novel high molecular weight (M n = (3.4–21.0) × 104) ionic polyurethanes (PUs) have been prepared using four different ionic diols based on ammonium, quinuclidinium, diquinuclidinium and imidazolium cations. Furthermore, a range of ionic PUs bearing 13 different counteranions including classical ((CF3SO2)2N, BF4, PF6, and N(CN)2) and less encountered anionic species such as acetate, lactate, tetracyanoborate, bis(pentafluoroethylsulfonyl)amide, CF3SO2–N–CN and MeHal n (Me = Fe(III), Cu(II), Zn(II), Hal = Cl, Br) was obtained through the ion exchange reactions using the same bromide PU precursor. This allowed to separately isolate the effect of diisocyanate, cations and anions nature on physical properties of ionic PUs. The obtained poly(ionic liquid)s demonstrate high thermal stability (up to 275 °C), have glass transition temperatures in the range of 30–78 °C and show remarkable CO2 capture. It was found that ionic PUs incorporating diquinuclidinium cation and CH3COO or BF4 anions exhibit the highest CO2 sorption (18.25 and 24.76 mg/g at 273 K and 1 bar), not only overcoming the CO2 capture reported to date for linear PILs, but even surpassing the highest value known for cross-linked meso-porous poly(ionic liquid)s (20.24 mg/g at 273 K and 1 bar). Altogether, this paper demonstrates the potential of poly(ionic liquid)s as efficient designing materials for CO2 capture.
Polymer hydrogels exhibit actuation properties that result in reversible shape transformations and have promising applications in soft robotics, drug delivery systems, sensors, and microfluidic devices. Actuation occurs due to differential hydrogel swelling and is generally achieved by modulating hydrogel composition. Here a different approach to hydrogel actuation that originates solely from its structural anisotropy is reported. For 3D-printed single-layer hydrogels formed by cellulose nanocrystals (CNCs) and gelatin methacryloyl it is shown that shear-induced orientation of CNCs results in anisotropic mechanical and swelling properties of the hydrogel. Upon swelling in water, planar hydrogels acquire multiple complex 3D shapes that are achieved by i) varying CNC orientation with respect to the shape on the hydrogel sheet and ii) patterning the hydrogel with the regions of shearmediated and random CNC orientation. This study shows the capability to generate multiple shapes from the same hydrogel actuator based on the degree of its structural anisotropy. In addition, it introduces a biocompatible nanocolloidal ink with shear-thinning and self-healing properties for additive manufacturing of hydrogel actuators.
Titanium dioxide (TiO 2 ) is one of the most widely used materials in resistive switching applications, including random-access memory, neuromorphic computing, biohybrid interfaces, and sensors. Most of these applications are still at an early stage of development and have technological challenges and a lack of fundamental comprehension. Furthermore, the functional memristive properties of TiO 2 thin films are heavily dependent on their processing methods, including the synthesis, fabrication, and post-fabrication treatment. Here, we outline and summarize the key milestone achievements, recent advances, and challenges related to the synthesis, technology, and applications of memristive TiO 2 . Following a brief introduction, we provide an overview of the major areas of application of TiO 2 -based memristive devices and discuss their synthesis, fabrication, and post-fabrication processing, as well as their functional properties.
Currently, the chemistry of organofluorine compounds is a leading and rapidly developing area of organic chemistry. Fluorine present in a molecule largely determines its specific chemical and biological properties. This thematic issue covers the trends of organofluorine chemistry that have been actively developed in Russia the last 15 – 20 years. The review describes nucleophilic substitution and heterocyclization reactions involving fluorinated arenes and quinones and skeletal cationoid rearrangements in the polyfluoroarene series. The transformations involving CF3-substituted carbocations and radical cations are considered. Heterocyclization and oxidative addition reactions of trifluoroacetamide derivatives and transformations of the organic moiety in polyfluorinated organoboranes and borates with retention of the carbon – boron bond are discussed. Particular attention is devoted to catalytic olefination using freons as an efficient synthetic route to fluorinated compounds. The application of unsymmetrical fluorine-containing N-heterocyclic carbene ligands as catalysts for olefin metathesis is demonstrated. A variety of classes of organofluorine compounds are considered, in particular, polyfluorinated arenes and 1,2-diaminobenzenes, 1-halo-2-trifluoroacetylacetylenes, α-fluoronitro compounds, fluorinated heterocycles, 2-hydrazinylidene-1,3-dicarbonyl derivatives, imines and silanes. The potential practical applications of organofluorine compounds in fundamental organic chemistry, materials science and biomedicine are outlined. The bibliography includes 1019 references.
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