-Diethylhexyloxyphenylene benzothiadiazole paracyclophane-1,9-diene as a mixture of diastereomers was synthesized by a sequential benzyne-induced Stevens rearrangement, oxidation and pyrolysis of a ...dithia3.3paracyclophane. Reaction of these highly strained cyclophanedienes with the second generation Grubbs catalyst showed that they can be ring opened to alternating
,
-phenylenevinylene polymers.
NMR experiments showed that one isomer 8a polymerised to 90% conversion, whereas the other 8b gave only 9% conversion due to steric hindrance on both faces of the alkene bridges of this isomer. The resulting polymers can be readily isomerized in dilute solution using visible light to the all-
isomer and the optical and electrochemical properties of these polymers were examined by theory and experiment.
Quantitative measurements of molecular dynamics at the solid–liquid interface are of crucial importance in a wide range of fields, such as heterogeneous catalysis, energy storage, nanofluidics, ...biosensing, and crystallization. In particular, the molecular dynamics associated with nucleation and crystal growth is very challenging to study because of the poor sensitivity or limited spatial/temporal resolution of the most widely used analytical techniques. We demonstrate that electrolyte-gated organic field-effect transistors (EGOFETs) are able to monitor in real-time the crystallization process in an evaporating droplet. The high sensitivity of these devices at the solid–liquid interface, through the electrical double layer and signal amplification, enables the quantification of changes in solute concentration over time and the transport rate of molecules at the solid–liquid interface during crystallization. Our results show that EGOFETs offer a highly sensitive and powerful, yet simple approach to investigate the molecular dynamics of compounds crystallizing from water.
The highly strained ortho-diethylhexyloxy 2.2paracyclophane-1,9-diene (M1) can be synthesized by ring contraction of a dithia3.3paracyclophane using a benzyne-induced Stevens rearrangement. This ...paracyclophanediene undergoes ring-opening metathesis polymerization to give well-defined 2,3-dialkoxyphenylenevinylene polymers with an alternating cis/trans alkene stereochemistry and controllable molecular weight. Fully conjugated block copolymers with electron-rich and electron-deficient phenylene vinylene polymer segments can be prepared by sequential monomer additions. These polymers can be readily isomerized to the all-trans stereochemistry polymer. The optical and electrochemical properties of these polymers were investigated by theory and experiment.
A modular approach to underexplored, unsymmetrical 1benzothieno3,2-
b
1benzothiophene (BTBT) scaffolds delivers a library of BTBT materials from readily available coupling partners by combining a ...transition-metal free Pummerer CH-CH-type cross-coupling and a Newman-Kwart reaction. This effective approach to unsymmetrical BTBT materials has allowed their properties to be studied. In particular, tuning the functional groups on the BTBT scaffold allows the solid-state assembly and molecular orbital energy levels to be modulated. Investigation of the charge transport properties of BTBT-containing small-molecule:polymer blends revealed the importance of molecular ordering during phase segregation and matching the highest occupied molecular orbital energy level with that of the semiconducting polymer binder, polyindacenodithiophene-benzothiadiazole (PIDTBT). The hole mobilities extracted from transistors fabricated using blends of PIDTBT with phenyl or methoxy functionalized unsymmetrical BTBTs were double those measured for devices fabricated using pristine PIDTBT. This study underscores the value of the synthetic methodology in providing a platform from which to study structure-property relationships in an underrepresented family of unsymmetrical BTBT molecular semiconductors.
A modular approach to underexplored, unsymmetrical 1benzothieno3,2-
b
1benzothiophene (BTBT) scaffolds, combining a transition-metal free Pummerer CH-CH-type cross-coupling and a Newman-Kwart reaction, delivers a library of BTBT materials.
LOV-domains are ubiquitous photosensory proteins that are commonly re-engineered to serve as powerful and versatile fluorescent proteins and optogenetic tools. The photoactive, flavin chromophore, ...however, is excited using short wavelengths of light in the blue and UV regions, which have limited penetration into biological samples and can cause photodamage. Here, we have used non-linear spectroscopy and microscopy of the fluorescent protein, iLOV, to reveal that functional variants of LOV can be activated to great effect by two non-resonant photons of lower energy, near infrared light, not only in solution but also in biological samples. The two photon cross section of iLOV has a significantly blue-shifted S0 → S1 transition compared with the one photon absorption spectrum, suggesting preferential population of excited vibronic states. It is highly likely, therefore, that the two photon absorption wavelength of engineered, LOV-based tools is tuneable. We also demonstrate for the first time two photon imaging using iLOV in human epithelial kidney cells. Consequently, two photon absorption by engineered, flavin-based bio-molecular tools can enable non-invasive activation with high depth resolution and the potential for not only improved image clarity but also enhanced spatiotemporal control for optogenetic applications.
Organic semiconductors (OSCs) promise to deliver next‐generation electronic and energy devices that are flexible, scalable and printable. Unfortunately, realizing this opportunity is hampered by ...increasing concerns about the use of volatile organic compounds (VOCs), particularly toxic halogenated solvents that are detrimental to the environment and human health. Here, a cradle‐to‐grave process is reported to achieve high performance p‐ and n‐type OSC devices based on indacenodithiophene and diketopyrrolopyrrole semiconducting polymers that utilizes aqueous‐processes, fewer steps, lower reaction temperatures, a significant reduction in VOCs (>99%) and avoids all halogenated solvents. The process involves an aqueous mini‐emulsion polymerization that generates a surfactant‐stabilized aqueous dispersion of OSC nanoparticles at sufficient concentration to permit direct aqueous processing into thin films for use in organic field‐effect transistors. Promisingly, the performance of these devices is comparable to those prepared using conventional synthesis and processing procedures optimized for large amounts of VOCs and halogenated solvents. Ultimately, the holistic approach reported addresses the environmental issues and enables a viable guideline for the delivery of future OSC devices using only aqueous media for synthesis, purification and thin‐film processing.
An environmentally benign cradle‐to‐grave process from synthesis‐to‐device is demonstrated for high performance organic field‐effect transistors. This holistic approach uses aqueous processes from mini‐emulsion polymerization to purification and thin‐film deposition. Compared to conventional approaches, the process requires fewer steps, lower reaction temperatures, a significant reduction in the use of volatile organic compounds and avoids toxic halogenated solvents.
In this work, the effect of pulsed laser used during the powder bed fusion (L-PBF) additive manufacturing (AM) process on Inconel 718 (IN718) material properties has been investigated. Argon gas ...atomised (AGA) IN718 powder is characterised in terms of flow, density, particle size distribution and morphology. Powder shows mostly spherical morphology with Hausner ratio of 1.17 indicating good flow characteristics. Density optimisation trials are carried out by varying laser power and exposure time. Fabricated samples are characterised in terms of porosity by area fraction analysis using light microscopy and volume fraction analysis using X-ray microcomputed tomography (micro-CT). Minimum porosity of 0.16% is achieved for laser power of 200 W and exposure time of 110 μs Microstructural analysis using the Electron Backscatter Diffraction (EBSD) technique shows limited columnar grain structure in the Z direction and more equiaxed type grains in the XY direction (normal to the Z direction). Tensile test results show 754 MPa yield strength, 1070 MPa ultimate tensile strength and ~24% elongation. Finally, hole drilling residual stress measurements show increase from ~0 MPa to over 450 MPa in tensile stress up to a depth of 1 mm from the top surface of the as-build L-PBF IN718 sample. It has been found that laser pulsing produces higher homogeneity in grain structure and better mechanical properties than that by the continuous laser method.
The cyclic dynamic loading behaviour of a multilayer TiAlSiN coating on M2 steel was systematically investigated using repetitive nano-impact over a wide range of impact load. Its behaviour was ...compared with a monolayer TiN on the same substrate. When the load was increased to 10mN and 30mN for the TiN and TiAlSiN coatings, respectively, cracks started to appear during the tests demonstrated as depth steps in the impact depth curves. The improved crack resistance of TiAlSiN coating is consistent with its higher H/Er and H3/Er2 measured by nanoindentation. The impact footprints were studied from both top-view and cross-sectional view using a focused ion beam microscope and SEM. Spallation was observed in both coatings at higher impact loads. TiAlSiN coating shows much less spallation due to its multilayer structure. The cross-sectional study discovered that the cracks were initiated within the coating. A simple model has been used to study the power law relationship between the impact volume loss and the impact velocity.
► A systematic study of the effect of nano-impact force. ► FIB/SEM was used to study the cross-sectional and top views of the impact footprints. ► At low loads, TiAlSiN showed improved crack resistance consistent with its higher H/Er and H3/Er2. ► At high loads, TiAlSiN showed much less spallation due to its multilayer structure. ► A simple model to study the power law relationship between the volume loss and the velocity.
The powder's characteristics and its purity can greatly influence the properties of nickel (Ni)-base superalloys parts produced by near net-shape powder metallurgy hot isostatic pressing (NNS PM HIP) ...manufacturing process. In this study, Inconel 625 (IN625) powders produced using four different atomisation routes, argon, nitrogen, plasma and water atomisation (AGA, NGA, PA, WA, respectively) were investigated. The first section of this study is focused on the determination of powder characteristics which includes chemical composition, particle size distribution (PSD), tap density and powder's cross-section analysis, whereas the second section is about hot isostatic pressing (HIPping) of the four powder types and to assess the impact of the powder characteristics on the microstructure-property development after HIPping. To gain an understanding of the surface chemistry of the powders, X-ray photoelectron spectroscopy (XPS) analysis were carried out on the surface of the four powders. The latter analysis highlighted fundamental differences on the powder's surface, especially the differences in the surface and near-surface distribution of the alloying elements i.e. C, O, Cr, Mo and Nb present in the alloy chemistry. The micrographs of the four IN625 hot isostatically pressed (HIPped) powders revealed a fully dense microstructure with the presence of prior particle boundaries (PPBs). The atomisation route greatly impacted the nature and amount of PPBs, as well as on the fractions and sizes of oxides, carbides, oxycarbides and oxycarbonitrides precipitates. WA showed the most severe presence of PPBs, followed by NGA, AGA and lastly PA. The powder quality has a greater impact on the mechanical properties of as-HIPped materials, especially on ductility. Overall, PA HIPped IN625 possessed the optimum balance between tensile strength, ductility and Charpy impact properties once compared to the others and match the properties to wrought IN625 material.
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The aim of this work is to determine the impact of post-thermal treatments on the mechanical properties and microstructure of alloy 718 superalloy manufactured through modulated laser powder bed ...fusion. Three post-thermal treatments at 980 °C and 1200 °C with and without hot isostatic pressing are utilised, followed by standard ageing procedure. The tensile mechanical properties, microstructure, crystallography, morphology, fracture impact and hardness after each heat treatment are determined. It has been found that the heat treatment procedure at 980 °C significantly affects the tensile properties while leading to no change in grain size or orientation, and formation of twined grains. A temperature of 1200 °C with and without pressure causes considerable grain growth in comparison with the as-built and 980 conditions and significant formation of twinned grains. Hot isostatic pressing was found to produce the tensile mechanical properties close to those of wrought alloy 718.
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