Naphthalene-2,3-diylbis[(2-thien­yl)methanone]

The asymmetric unit of the title compound, C20H12O2S2, contains two crystallographically independent mol­ecules which differ in the orientations of thienylmethanone units with respect to the naphthalene ring system [dihedral angles of 65.30 (11) and 50.94 (11)° in one molecule, 41.94 (12) and 69.61 (13)° in the other]. The crystal structure is stabilized by C—H⋯O and C—H⋯π inter­actions

5,7-Bis(1-benzothio­phen-2-yl)-2,3-dihydro­thieno[3,4-b][1,4]dioxine

In the title compound, C22H14O2S3, the dioxane ring is disordered over two sites [site occupancies = 0.623 (3) and 0.377 (3)]; both components adopt half-chair conformations. The two benzothio­phene ring systems are asymmetrically twisted away from the attached thio­phene ring [dihedral angles = 20.57 (3) and 6.70 (3)°] and are oriented at an angle of 26.83 (3)°. No significant hydrogen bonding or π–π inter­actions are observed in the crystal structure

Conductive liquid metal elastomer thin films with multifunctional electro-mechanical properties

Wearable electronics, conformable sensors, and soft/micro-robotics require conductive yet stretchable thin films. However, traditional free standing metallic thin films are often brittle, inextensible, and must be processed in strict environments. This limits implementation into soft technologies where high electrical conductivity must be achieved while maintaining high compliance and conformability. Here we show a liquid metal elastomeric thin film (LET) composite with elastomer-like compliance (modulus \u3c 500 kPa) and stretchability (\u3e 700%) with metallic conductivity (sheet resistance \u3c 0.1 Ω/square). These 30-70 um thin films are highly conformable, free standing, and display a unique Janus microstructure, where a fully conductive activated side is accompanied with an opposite insulated face. LETs display exceptional electro-mechanical characteristics, with a highly linear strain-resistance relationship beyond 700% deformation while maintaining a low resistance. We demonstrate the multifunctionality of LETs for soft technologies by leveraging the unique combination of high compliance and electrical conductivity with transfer capabilities for strain sensing on soft materials, as compliant electrodes in dielectric elastomeric actuator (DEA), and as resistive heaters for liquid crystal elastomer (LCE)

Energy Level Manipulation of Semiconducting Polymers via Cyano and Alkoxy Substituents for Polymer Solar Cells

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A survey on cognitive radio network attack mitigation using machine learning and blockchain

Abstract Cognitive radio network is a promising technology to enhance the spectrum utilization and to resolve the spectrum scarcity issues. But the malicious users play havoc with the network during spectrum sensing and demean the network performance. It is mandatory to identify such malicious attacks and address it. There have been many traditional methods to mitigate the cognitive radio network attacks. In this paper, we have surveyed advanced attack mitigation techniques like machine learning, deep learning and blockchain. Thus, by detecting and addressing the malicious activities, the throughput and overall network performance can be improved

Steering with light: indexable photomotility in liquid crystalline polymers

Harnessing light to achieve manipulation and motility in meso and mm-scale systems offers the ability to remotely trigger actuation without requiring on-board power. Central to achieving macroscopic photomotility is the generation of asymmetric interaction between the light-responsive actuator and a substrate. Here, we demonstrate a facile route for achieving indexable, stepped translation of structures fabricated from azobenzene-functionalize liquid crystalline polymers (ALCP). The symmetry breaking in the dynamics of coiling (during irradiation) and uncoiling (when the light is turned off) as a function of the director orientation in splayed ALCP strips leads to asymmetric reaction forces in the interaction with a surface. The broken symmetry leads to directional translation of the center of mass in discrete steps for each on/off cycle of irradiation. Creating composite structures offers a route for hard-coding the trajectories of motility across a range of trajectories that are either rectilinear or curvilinear. Expanding this approach can offer a framework for achieving steerable light-powered microrobots that can translate on arbitrary surface topographies

Conductive liquid metal elastomer thin films with multifunctional electro-mechanical properties

Wearable electronics, conformable sensors, and soft/micro-robotics require conductive yet stretchable thin films. However, traditional free standing metallic thin films are often brittle, inextensible, and must be processed in strict environments. This limits implementation into soft technologies where high electrical conductivity must be achieved while maintaining high compliance and conformability. Here we show a liquid metal elastomeric thin film (LET) composite with elastomer-like compliance (modulus 700%) with metallic conductivity (sheet resistance This is a peer-reviewed, un-copyedited version of an article accepted for publication/published in Multifunctional Materials. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. DOI: 10.1088/2399-7532/abbc66. Posted with permission.</p

Energy Level Engineering of Donor Polymers via Inductive and Resonance Effects for Polymer Solar Cells: Effects of Cyano and Alkoxy Substituents

Fine tuning the energy levels of donor polymers is a critically important step toward achieving high power conversion efficiencies in polymer solar cells (PSCs). We systematically controlled the energy levels of donor polymers by introducing cyano (CN) and alkoxy (OR) groups into the 4,4′-didodecyl-2,2′-bithiophene (BT) unit in a step-by-step fashion, thereby varying the inductive and resonance effects. The three monomer units (BT, BTC, and BTCox) were polymerized with benzo­[1,2-b:4,5-<i>b</i>′]­dithiophene (BDT) as a counter unit to afford three polymers (PBDT-BT, PBDT-BTC, and PBDT-BTCox). The highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels decreased significantly upon the introduction of CN groups, and these levels increased slightly upon attachment of the OR groups, in good agreement with the measured open-circuit voltages of the three polymer devices. The strong inductive and resonance effects present in PBDT-BTCox narrowed the polymer band gap to 1.74 eV to afford a power conversion efficiency of 5.06%, the highest value achieved among the three polymers

Medium-Bandgap Conjugated Polymers Containing Fused Dithienobenzochalcogenadiazoles: Chalcogen Atom Effects on Organic Photovoltaics

We designed, synthesized, and characterized a series of three medium-bandgap conjugated polymers (PBDT­fDTBO, PBDT­fDTBT, and PBDT­fDTBS) consisting of fused dithienobenzo­chalcogenadiazole (fDTBX)-based weak electron-deficient and planar building blocks, which possess bandgaps of ∼2.01 eV. The fDTBX-based medium-bandgap polymers exhibit deep-lying HOMO levels (∼5.51 eV), which is beneficial for use in multijunction polymer solar cell applications. The resulting polymers with chalcogen atomic substitutions revealed that the difference in the electron negativity and atomic size of heavy atoms highly affects an intrinsic property, morphological feature, and photovoltaic property in polymer solar cells. The polymer solar cells based on sulfur-substituted medium-bandgap polymer showed power conversion efficiencies above 6% when blended with [6,6]-phenyl-C₇₁-butyric acid methyl ester in a typical bulk-heterojunction single cell. These results suggest that the fDTBX-based medium-bandgap polymer is a promising alternative material for P3HT in tandem polymer solar cells for achieving high efficiency