A paradigm-shifting design strategy is demonstrated that unifies the treatment of electronic and conformational properties of polymer dielectrics for concurrent high electric field and elevated temperature harsh conditions.

Flexible large bandgap dielectric materials exhibiting ultra-fast charging-discharging rates are key components for electrification under extremely high electric fields. A polyoxafluoronorbornene (m-POFNB) with fused five-membered rings separated by alkenes and flexible single bonds as the backbone, rather than conjugated aromatic structure typically for conventional high-temperature polymers, is designed to achieve simultaneously high thermal stability and large bandgap. In addition, an asymmetrically fluorinated aromatic pendant group extended from the fused bicyclic structure of the backbone imparts m-POFNB with enhanced dipolar relaxation and thus high dielectric constant without sacrificing the bandgap. m-POFNB thereby exhibits an unprecedentedly high discharged energy density of 7.44 J/cm3 and high efficiency at 150 °C. This work points to a strategy to break the paradox of mutually exclusive constraints between bandgap, dielectric constant, and thermal stability in the design of all-organic polymer dielectrics for harsh condition electrifications.

onto printed circuit designs, and printing all electronic components onto commercially available textiles. [4][5][6][7][8][9][10][11][12] Sporting goods companies have envisioned a clothing system with integrated touchscreen capabilities that combines functionality with convenience. [13] This clothing would monitor heart rate, record body temperature, and change color. Electrochromic fabrics, which change color upon application of an electric potential, [14] would give the user the ability to create their own designs and upload it directly to their clothing. For the military, a soldier's clothing could be constantly shifting to the most optimal color scheme as their surroundings change.Textile-based electrochromic devices, unlike most conjugated polymer based electrochromic devices, are reflective in nature. They consist of an electrochromic polymer-coated working electrode separated from a counter electrode by a layer of electrolytic gel. Invernale and co-workers reported the fabrication of color changing spandex using poly (3,4-ethylene dioxythiophene):poly (styrene sulfonate) (PEDOT: PSS) coated fabrics as electrodes and poly (BEDOT-T-Sil (Octyl) 2 ) as an electrochromic material. [15] The fabricated electrochromic devices showed a color change from blue to red with a switching speed of ≈15 s. The spandex based electrochromic fabric display (EFD) showed color change even when stretched to 20% of its dimensions though a decrease in color density was observed upon stretching. These devices, while flexible and stretchable, are dual layer devices which would result in a thicker, bulkier garment.The factors determining the expression of color and switching speed of a device are the conductivity of the material, the electrochemical potential window of the electrodes, and the color of the fabric on which the EFD is constructed. [16] In the case of PEDOT:PSS electrodes, the stable window is +/− 2 V. Recent studies on PEDOT:PSS based transmissive devices have shown that having the electrochromic material switch well below the window of the electrode increases the stability of the device. [15,17] For fabric devices, using an electrochromic polymer that switches at low voltages would reduce the expression of PEDOT:PSS in the overall color of the material. Invernale and co-workers investigated color transitions as a function of underlying fabric color and found that bright colors give greater electrochromic contrast than dark colors. [18] Current wearable technology is often bulky and restrictive to fluid movement. This work details a single-layer, hydrophobic, printed electrochromic textile that switches wirelessly from red to blue with a switching speed ≈30 s. Using a hole-through fabrication method, the flexible devices offer aesthetics to the display by concealing all electronic connections on their backsides while maintaining their "fabric" feel. First, an all organic electrochromic planar textile device is fabricated by screen printing commercially available poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) ...

Ultrafast infrared vibrational spectroscopy is widely used for the investigation of dynamics in systems from water to model membranes. Because the experimental observation window is limited to a few times the probe's vibrational lifetime, a frequent obstacle for the measurement of a broad time range is short molecular vibrational lifetimes (typically a few to tens of picoseconds). Five new longlifetime aromatic selenocyanate vibrational probes have been synthesized and their vibrational properties characterized. These probes are compared to commercial phenyl selenocyanate. The vibrational lifetimes range between ∼400 and 500 ps in complex solvents, which are some of the longest room-temperature vibrational lifetimes reported to date. In contrast to vibrations that are long-lived in simple solvents such as CCl 4 , but become much shorter in complex solvents, the probes discussed here have ∼400 ps lifetimes in complex solvents and even longer in simple solvents. One of them has a remarkable lifetime of 1235 ps in CCl 4 . These probes have a range of molecular sizes and geometries that can make them useful for placement into different complex materials due to steric reasons, and some of them have functionalities that enable their synthetic incorporation into larger molecules, such as industrial polymers. We investigated the effect of a range of electron-donating and electron-withdrawing para-substituents on the vibrational properties of the CN stretch. The probes have a solvent-independent linear relationship to the Hammett substituent parameter when evaluated with respect to the CN vibrational frequency and the ipso 13 C NMR chemical shift.

Dielectric polymers that can withstand harsh conditions of simultaneous high electric field and elevated temperature are widely used in electrical and electronic systems. However, traditionally, the thermal stability of polymers is engineered based on highly conjugated aromatic molecular structures, giving rise to soring charge transport and thus poor charge–discharge efficiency under concurrent high electric field and elevated temperature. Here, we locally improved the rotational flexibility of the phenylenediamine linkage structure in polyetherimide (PEI) to decouple the conjugation of the organic molecule. p-Phenylenediamine (5 mol %) as a low-energy rotation repeat unit within PEI significantly optimized its dielectric properties, exhibiting substantially suppressed electrical conduction (more than 1 order of magnitude lower) and polarization loss (<1%). The new PEI has a largely improved charge–discharge efficiency of 91% at 400 MV/m 200 °C, outperforming the best-reported polymer-based dielectrics without any modification of the cost of goods. The high-throughput facile processing of the new PEI provides a potential candidate for energy storage applications under elevated temperatures. This work unveils a scalable approach to exploring polymer dielectrics by introducing a small amount of local structural modifications.