In this report, a dipolar glass polymer, poly(2-(methylsulfonyl)ethyl methacrylate) (PMSEMA), was synthesized by free radical polymerization of the corresponding methacrylate monomer. Due to the large dipole moment (4.25 D) and small size of the side-chain sulfone groups, PMSEMA exhibited a strong γ transition at a temperature as low as -110 °C at 1 Hz, about 220 °C below its glass transition temperature around 109 °C. Because of this strong γ dipole relaxation, the glassy PMSEMA sample exhibited a high dielectric constant of 11.4 and a low dissipation factor (tan δ) of 0.02 at 25 °C and 1 Hz. From an electric displacement-electric field (D-E) loop study, PMSEMA demonstrated a high discharge energy density of 4.54 J/cm(3) at 283 MV/m, nearly 3 times that of an analogue polymer, poly(methyl methacrylate) (PMMA). However, the hysteresis loss was only 1/3-1/2 of that for PMMA. This study suggests that dipolar glass polymers with large dipole moments and small-sized dipolar side groups are promising candidates for high energy density and low loss dielectric applications.

A set of 12 new polyimides (PIs) with one or three polar CN dipoles directly attached to the aromatic diamine part were synthesized and their electric energy storage properties were studied using broadband dielectric spectroscopy (BDS) and electric displacement-electric field (D-E) loop measurements to determine their potential for high temperature film capacitors for aerospace applications. It was found that adding highly polar nitrile groups to the PI structure increased permittivity and thus electrical energy storage, especially at high temperatures, and 3 CN dipoles were better than 1 CN dipole. Below the glass transition temperature (T g ), a weak g transition was observed around À100 C and a broad b transition was observed between 100 and 150 C. It was the b (i.e., precursor dipolar motion before long-range segmental motion, or glass transition), rather than the g sub-T g transition that substantially increased the permittivity of PIs. From the BDS results on PIs having 3 nitrile groups, the enhancement in permittivity from permanent dipoles decreased with dianhydride in the order of pyromellitic dianhydride (PMDA) > 4,4 0 -oxydiphthalic dianhydride (OPDA) > 1,1,1,3,3,3hexafluoropropane dianhydride (6FDA) > 4,4 0 -benzophenonetetracarboxylic dianhydride (BTDA). Meanwhile, the increase in permittivity also decreased in the order of para-para, meta-para, and meta-meta linkage in the diamine, suggesting that the para-para linkage favored easier dipole rotation than the meta-meta linkage.From the D-E loop study, the PIs with a combination of PMDA dianhydride and a para-para linkage exhibited the highest discharged energy density and a reasonably low loss. † Electronic supplementary information (ESI) available: Syntheses of monomers and polymers, reection and transmission X-ray diffraction proles, details of calculation, and BDS results for sample 2a. See

Interfacial polarization due to space charges enhances electrical insulation and thus breakdown strength for multilayer polymer films.

Three new isomeric diamines containing three, oxylinked benzonitriles (3BCN), one of which is asymmetric (meta, para, or m, p), are synthesized in a 3-step sequence. Polycondensation of these diamines and four common dianhydrides (6FDA, OPDA, BTDA, and PMDA) in N,N-dimethylacetamide via poly(amic acid) precursors and thermal curing at temperatures up to 300 C lead to three series of tough, creasable polyimide (PI) films (tensile moduli 5 1.63 2 2.86 GPa). Among these PIs, two PMDA-based PIs possess relatively high crystallinity and two OPDA-based PIs, low crystallinity, whereas all 6FDA-and BTDA-based PIs, and m,m-3BCN-OPDA-PI are amorphous, readily soluble in common polar aprotic solvents. Thermally stable and having high T g (216 2 341 C), these PIs lose 5% weight around 493-503 C in air and 463-492 C in nitrogen. Dielectric properties have been evaluated by broadband dielec-tric spectroscopy (BDS) and electric displacement-electric-field (D-E) loop measurements. D-E loop results show an increase in high temperature permittivity (at 190 C/1 kHz) from 2.9 (for parent PI CP2 with no nitrile group) to as high as 4.9 for these PIs, while keeping their dielectric loss relatively low. Thus, an increase in dipole moment density by the presence of three neighboring CN per repeat unit can increase the overall permittivity, which could be further enhanced by sub-T g mobility of para-phenylene linkages (BDS results). Published 2014. † J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 422-436

Current development of advanced power electronics for electric vehicles demands high temperature, high energy density, and low loss polymer dielectrics. Multilayer films (MLFs), which are comprised of alternating high temperature/low loss linear dielectric polymer such as polysulfone (PSF) and high energy density polymer such as poly(vinylidene fluoride) (PVDF), are promising for this application, because high temperature tolerance, high energy density, and low loss can be achieved simultaneously. This study explored the reduction of impurity ion conduction loss in PSF/ PVDF MLFs (e.g., the dissipation factor is as low as 0.003 at 1 Hz and 100 °C) without sacrificing high dielectric constant and high energy density. Various electric poling processes were explored at a temperature slightly below the glass transition temperature (T g ∼ 185 °C) of PSF. Compared with pure alternating current (AC) and pure direct current (DC) poling methods, unipolar (DC + AC) poling was found to be the most effective in polarizing impurity ions from the PVDF layers into the PSF layers. Because of the low segmental mobility below T g , impurity ions were largely "locked" in PSF. The immobilization of impurity ions was thermally stable up to 120 °C. Because DC-link capacitors work with unipolar charge and discharge processes, these PSF/PVDF MLFs with low dielectric losses are promising for the application of advanced power electronics for the automobile industry.

To search for alternative electrostrictive polymers and to understand the underlying mechanism, the structure‐ferroelectric/electrostrictive property relationship for nylon‐12‐based poly(ether‐b‐amide) multiblock copolymers (PEBAX) is investigated. Two PEBAX samples are studied, namely, P6333 and P7033 with 37 and 25 mol.% of soft poly(tetramethylene oxide) (PTMO) blocks, respectively. In both samples, poorly hydrogen‐bonded mesophase facilitates electric field‐induced ferroelectric switching. Meanwhile, the longitudinal electrostrictive strain (S1)–electric field (E) loops are obtained at 2 Hz. Different from conventional poly(vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)]‐based terpolymers, uniaxially stretched nylon‐12‐based PEBAX samples exhibit negative S1, that is, shrinking rather than elongation in the longitudinal direction. This is attributed to the unique conformation transformation of nylon‐12 crystals during ferroelectric switching. Namely, at a zero electric field, crystalline nylon‐12 chains adopt a more or less antiparallel arrangement of amide groups. Upon high‐field poling, ferroelectric domains are enforced with more twisted chains adopting a parallel arrangement of amide groups. Meanwhile, extensional S1 is observed for P6333 at electric fields above 150 MV m−1. This is attributed to the elongation of the amorphous phases (i.e., amorphous nylon‐12 and PTMO). Therefore, competition between shrinking S1 from mesomorphic nylon‐12 crystals (i.e., nanoactuation) and elongational S1 from amorphous phases determines the ultimate electrostriction behavior in stretched PEBAX films.

A porous Teflon ring|solid disk electrode is herein described specifically designed for acquiring online mass spectrometric measurements under well-defined forced convection created by liquid emerging from a circular nozzle impinging on the disk under wall-jet conditions. Measurements were performed for the oxidation of hydrazine, N(2)H(4), in a deaerated phosphate buffer electrolyte (pH 7) on Au, a process known to yield dinitrogen as the product. The N(2)(+) ion currents, measured by the mass spectrometer, i(N(2)(+)), as well as the corresponding polarization curves recorded simultaneously displayed very similar s-like shapes when plotted as a function of the potential applied to the Au disk. In fact, the limiting currents observed both electrochemically and spectrometrically were found to be proportional to [N(2)H(4)]. However, the limiting values of i(N(2)(+)) did not increase monotonically with the flow rate, ν(f), reaching instead a maximum and then decreasing to values independent of ν(f). This behavior has been attributed in part to hindrances in the mass transport of gases through the porous materials.

The authors have analyzed the content of about a dozen physical chemistry textbooks regarded as among the most commonly used by undergraduate educators in the U.S. to identify the extent and quality of the material therein covered in the specific area of physical electrochemistry. It is recommended that the textbook writers should take advantage of material treated in its most fundamental forms, and find means to extend it to modern technological applications. Examples would include extensions of the Debye Hückel theory of electrolytes to interfacial charging of ideal polarizable electrodes, a concept that relates directly to the operation of electrochemical double layer capacitors as energy storage devices found in container port cranes around the globe. Also long overdue is the use of lithium ion batteries as examples that should replace the Weston or Daniell's voltaic piles, as well as the broad introduction of proton exchange membrane electrolyte based fuel cells instead of their historical liquid based predecessors. The copious resources of material available on the Web should be also used.