Mechanically Driven Activation of Polyaniline into Its Conductive Form

Experimental and DFT studies of porous carbon covalently functionalized by polyaniline as a corrosion inhibition barrier on nickel-based alloys in acidic media

In acidic medium, nickel alloys severely suffer from long term corrosion problems as a result of the breakdown of their passivating oxide. The present study considers polyaniline functionalized fish-scale graphitic carbon as an anticorrosion coating on the nickel alloy surface. The fish-scale porous carbon materials are characterized by XRD, ATR-FITR, UV, Raman, TGA, SS NMR, FESEM, and TEM methods. The surface of the alloy is covalently bound with a polyaniline long chain protonated polymer so that the polyaniline functionalized honeycomb fish-scale carbon structure can exchange electrons with the metal surface. The corrosion inhibition efficiency has been investigated in different acid media like sulfuric acid and hydrochloric acid by electrochemical methods. Polyaniline functionalized porous carbon showed in 1 M H₂SO₄ inhibition efficiency around 64% and in 1 M HCl inhibition efficiency was around 74%. The inhibition efficiency was higher in HCl because chloride ions were not able to penetrate the graphitic sheet. The novelty of this coating is in the fact that the polyaniline functionalized porous carbon has high conductivity and is electrochemically stable in acidic medium. It is able to donate electrons to the polarized metal surface.

Polyaniline functionalized fish scale carbon chemisorption on 111 nickel alloy surface by polyaniline polaron nitrogen free electron.

Mechanical Control of Periodic Precipitation in Stretchable Gels to Retrieve Information on Elastic Deformation and for the Complex Patterning of Matter

Material design using nonequilibrium systems provides straightforward access to complexity levels that are possible through dynamic processes. Pattern formation through nonequilibrium processes and reaction-diffusion can be used to achieve this goal. Liesegang patterns (LPs) are a kind of periodic precipitation patterns formed through reaction-diffusion. So far, it has been shown that the periodic band structure of LPs and the geometry of the pattern can be controlled by experimental conditions and external fields (e.g., electrical or magnetic). However, there are no examples of these systems being used to retrieve information about the changes in the environment as they form, and there are no studies making use of these patterns for complex material preparation. This work shows the formation of LPs by a diffusion-precipitation reaction in a stretchable hydrogel and the control of the obtained patterns by the unprecedented and uncommon method of mechanical input. Additionally, how to use this protocol and how deviations from "LP behavior" of the patterns can be used to "write and store" information about the time, duration, extent, and direction of gel deformation are presented. Finally, an example of using complex patterning to deposit polypyrrole by using precipitation patterns is shown as a template.

Mechanochemical and slow-chemistry radical transformations: a case of diorganozinc compounds and TEMPO

From the green chemistry perspective, molecular solid-state transformations conducted under mild conditions are of great interest and desirability. However, research in this area lacked popularity in the previous century, and thus progressed slowly. In particular, the application of radical reactions in solid-state chemistry has been hampered by several long-standing challenges that are intrinsically associated with the apparent unpredictable nature of radical chemistry. We present a comparative study of model mechanochemical, slow-chemistry and solution radical reactions between TEMPO and homoleptic organozinc compounds (i.e., di-tert-butylzinc and diphenylzinc). In the case of the tBu2Zn/TEMPO reaction system only a dimeric diamagnetic complex [tBuZn(μ-TEMPO*)]2 is obtained in yields slightly varying with the method chosen. In contrast, when TEMPO is mixed with diphenylzinc in a 2 : 1 molar ratio a novel paramagnetic Lewis acid-base adduct [[Ph2Zn(η1-TEMPO)]·TEMPO] is isolated in high yields regardless of the applied methodology. This adduct is also formed in the slow-chemistry process when TEMPO is gently mixed with Ph2Zn in a 1 : 1 molar ratio and left for two weeks at ambient temperature. Within the next week the reaction mixture gives in high yield a diamagnetic dinuclear compound [PhZn(μ-TEMPO*)][PhZn(μ2-η1:η1-TEMPO*)] and biphenyl. The analogous reaction conducted in toluene results in a much lower conversion rate. The reported results open up a new horizon in molecular solid-state radical transformations.

Control of triboelectric charges on common polymers by photoexcitation of organic dyes

Triboelectric charging of insulators, also known as contact charging in which electrical charges develop on surfaces upon contact, is a significant problem that is especially critical for various industries such as polymers, pharmaceuticals, electronics, and space. Several methods of tribocharge mitigation exist in practice; however, none can reach the practicality of using light in the process. Here we show a light-controlled manipulation of triboelectric charges on common polymers, in which the tribocharges are mitigated upon illumination with appropriate wavelengths of light in presence of a mediator organic dye. Our method provides spatial and temporal control of mitigation of static charges on common polymer surfaces by a mechanism that involves photoexcitation of organic dyes, which also allows additional control using wavelength. This control over charge mitigation provides a way to manipulate macroscopic objects by tribocharging followed by light-controlled discharging.

Contact charging of insulators is a significant problem for various industries, such as plastics, electronics, and space. Here the authors gain spatial and temporal control of discharge of triboelectrically charged polymers upon illumination of a set of common organic dyes.

Repeatable mechanochemical activation of dynamic covalent bonds in thermoplastic elastomers

Repeated mechanical scission and recombination of dynamic covalent bonds incorporated in segmented polyurethane elastomers are demonstrated by utilizing a diarylbibenzofuranone-based mechanophore and by the design of the segmented polymer structures. The repeated mechanochemical reactions can accompany clear colouration and simultaneous fading.

Static Electricity-Responsive Supramolecular Assembly

Stimuli-responsive materials can convert between molecular scale and macroscopic scale phenomena. Two macroscopic static electricity-responsive phenomena based on nanoscale supramolecular assemblies of a zinc porphyrin derivative are presented. One example involves the movement of supramolecular assemblies in response to static electricity. The assembly of a pyridine (Py) complex of the above-mentioned derivative in cyclohexane is drawn to a positively charged material, whereas the assembly of a 3,5-dimethylpyridine complex is drawn to a negatively charged material. The second phenomenon involves the movement of a non-polar solvent in response to static electrical stimulation. A cyclohexane solution containing a small quantity of the Py-complexed assembly exhibited a strong movement response towards negatively charged materials. Based on spectroscopic measurements and electron microscope observations, it was revealed that the assembled formation generates the observed response to static electricity.

Dynamic covalent diarylbibenzofuranone-modified nanocellulose: mechanochromic behaviour and application in self-healing polymer composites

Surface mechanochemistry of nanocelluloses modified with a dynamic covalent mechanophore is investigated, and self-healing composites with the celluloses are developed.

Mechanochemical Tuning of the Binaphthyl Conformation at the Air-Water Interface

Gradual and reversible tuning of the torsion angle of an amphiphilic chiral binaphthyl, from -90° to -80°, was achieved by application of a mechanical force to its molecular monolayer at the air-water interface. This 2D interface was an ideal location for mechanochemistry for molecular tuning and its experimental and theoretical analysis, since this lowered dimension enables high orientation of molecules and large variation in the area. A small mechanical energy (<1 kcal mol(-1) ) was applied to the monolayer, causing a large variation (>50 %) in the area of the monolayer and modification of binaphthyl conformation. Single-molecule simulations revealed that mechanical energy was converted proportionally to torsional energy. Molecular dynamics simulations of the monolayer indicated that the global average torsion angle of a monolayer was gradually shifted.

Electrical Switchability and Dry-Wash Durability of Conductive Textiles

There is growing interest in the area of conductive textiles in the scientific and industrial community. Herein, we successfully prepared a conductive textile via covalently grafting polyaniline (PANI) onto cotton by a multi-step treatment process. The conductivity of the resultant fabric could be tuned by immersing in water having different pH values. The conductive and insulating properties of the textile could be conveniently switched by alternately immersing in acidic and alkaline bath solutions. Most importantly, the resultant conductive fabrics were able to withstand 40 simulated dry-wash cycles, with almost no decay in the electrical conductivity, indicating their excellent dry-wash durability. The present strategy for fabricating conductive fabrics with excellent switchability of electrical properties and dry-wash durability is expected to provide inspiration for the production of multifunctional conductive textiles for use in hash or sensitive conditions.

Mechanophores with a reversible radical system and freezing-induced mechanochemistry in polymer solutions and gels

Visualization and quantitative evaluation of covalent bond scission in polymeric materials are highly important for understanding failure, fatigue, and deterioration mechanisms and improving the lifetime, durability, toughness, and reliability of the materials. The diarylbibenzofuranone-based mechanophore radical system enabled, through electron paramagnetic resonance spectroscopy, in situ quantitative evaluation of scission of the mechanophores and estimation of mechanical energy induced along polymer chains by external forces. The coagulation of polymer solutions by freezing probably generated force but did not cleave the mechanophores. On the other hand, cross-linking led to efficient propagation of the force of more than 80 kJ mol(-1) to some mechanophores, resulting their cleavage and generation of colored stable radicals. This mechanoprobe concept has the potential to elucidate other debated issues in the polymer field as well.