An unprecedented azobenzene-based organic single-component ferroelectric

Organic single-component ferroelectrics, as an important class of metal-free ferroelectrics, are highly desirable because of their easy processing, mechanical flexibility, and biocompatibility. However, although nearly 50 years have passed since the discovery of photochromism in azobenzene-doped cholesteric liquid crystals, ferroelectricity has never been found in azobenzene-based crystals. Here, we use an amino group to substitute a fluorine atom of 2,2′,4,4′,6,6′-hexafluoroazobenzene, which successfully introduces ferroelectricity into 2-amino-2′,4,4′,6,6′-pentafluoroazobenzene (APFA). APFA shows an extremely high Curie temperature (T_c) of 443 K, which is outstanding among single-component ferroelectrics. It also exhibits an indirect optical band gap of 2.27 eV as well as photoisomerization behavior between the trans-form and the cis-form triggered by pedal motion. To our knowledge, APFA is the first azobenzene-based ferroelectric crystal. This work opens an avenue to design excellent single-component ferroelectrics and will inspire the exploration of azobenzene-based ferroelectrics for promising applications in biofriendly ferroelectric devices.

The first azobenzene-based organic single-component ferroelectric 2-amino-2′,4,4′,6,6′-pentafluoroazobenzene was designed, which shows an exceptionally high Curie temperature (T_c) of 443 K.     

An autosampler with a short transfer line for Curie point pyrolysis capillary gas chromatography

A new multichannel autosampler which can automatically analyze up to twenty samples in sequence has been developed for Curie point pyrolysis – capillary GC. Compared with a previous system [1] the transfer line between the pyroysis unit and chromatograph is shorter, and thus has less dead volume, and can be operated at a higher temperature (300 °C). The relative yields of higher boiling point, highly polar, and thermally labile pyrolysates generated from polymers, and the reproducibility, were better than those obtained from the previous autosampler. To facilitate rapid operation an additional flow controller is installed on the new device to shorten the time taken to purge air from the sampler.     

An organic ionic plastic crystal electrolyte based on the triflate anion exhibiting high proton transport

A novel organic ionic plastic crystal (OIPC) electrolyte based on a quaternary ammonium cation and the triflate anion has been synthesized, which shows fast proton transport and high thermal stability in the solid state when doped with triflic acid.     

An organic p-type dopant with high thermal stability for an organic semiconductor

To overcome the thermal instability of a p-doped organic hole transporting layer using the state-of-the-art p-type dopant, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, a potent electron accepter, 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane, has been found to possess superior thermal stability and proved to be an excellent p-type dopant.     

Lithium-doped,organic ionic plastic crystal electrolytes exhibiting high ambient-temperature conductivities

Film-forming, ionic plastic crystal—N,N-diethyl-N-methyl-N-(n-propyl)ammonium trifluoromethyltrifluoroborate (N₁₂₂₃[CF₃BF₃])—has been doped with Li[CF₃BF₃] salt to prepare stable Li-ion conducting plastic crystal electrolytes. Solid-state conductivities as high as 10⁻⁴–10⁻³ S cm⁻¹ have been obtained within the ambient-temperature plastic crystalline phase of the Li-doped materials. Solid-state Li deposition/dissolution based on these materials has been realized at 25 °C. The outstanding properties of these materials make them attractive candidates for all-solid-state Li batteries.     

Chromatographic profile of high boiling point organic acids in human urine

The profile of high boiling point organic acids in urine samples from both normal subjects and patients suspected of having some form of metabolic disorder has been determined by combined gas chromatography-mass spectrometry. Fifteen different compounds eluting after hippuric acid have been identified, including two, cinnamoylglycine and acetyltributylcitrate, which have not been recognised previously. Relative retention times and abbreviated mass spectra of the identified compounds are presented.     

Thermally induced processes in mixtures of aluminum with organic acids after plastic deformations under high pressure

DSC is used to measure the thermal effects of processes in mixtures of solid organic dibasic acids with powdered aluminum, subjected to plastic deformation under pressures in the range of 0.5–4.0 GPa using an anvil-type high-pressure setup. Analysis of thermograms obtained for the samples after plastic deformation suggests a correlation between the exothermal peaks observed around the temperatures of degradation of the acids and the thermally induced chemical reactions between products of acid degradation and freshly formed surfaces of aluminum particles. The release of heat in the mixtures begins at 30–40°C. The thermal effects in the mixtures of different acids change according to the order of acid reactivity in solutions. The extreme baric dependences of enthalpies of thermal effects are associated with the rearrangement of the electron subsystem of aluminum upon plastic deformation at high pressures.     

Structural characterization and Curie temperature determination of a sodium strontium niobate ferroelectric nanostructured powder

The Curie temperature and its correlation with the magnitude of the displacement of the niobium atom from the center of [NbO₆] octahedra in NaSr₂Nb₅O₁₅ nanostructured powder were investigated. A single powder was prepared by high-energy ball milling. A powder with an average crystallite size of 37 nm was prepared by calcining the precursor at 1423 K. The refinement of the structural parameters was carried out by the Rietveld method. NaSr₂Nb₅O₁₅ exhibits tetragonal symmetry with the tungsten bronze structure (a=b=12.3495 (6) Å, c=3.8911 (2) Å, V=593.432 (5) Å³, and Z=2). The site occupancy of the Na⁺ and Sr²⁺ cations and the interatomic distances between the niobium and oxygen atoms were derived. The [NbO₆] octahedron undergoes both rotation and tilting depending on the crystallographic site. The Curie temperature of the powder was derived using both the impedance and infrared spectroscopy methods.     

Curie point pyrolysis gas chromatography using ferromagnetic tubes as sample supports

Summary In pulse-mode pyrolysis gas chromatography, where a solid sample is pyrolysed by contact with a heated filament, there is usually no thermal equilibrium between sample and support. Such an equilibrium is approached by pyrolysing solid samples within ferromagnetic tubes. Tubes 1.5 mm outside diameter (10 % wall) may be heated and stabilized to the Curie Point (iron: 760 °C) in 60 msec. This type of Curie Point pyrolysis will help to increase reproducibility in pyrolysis gas chromatography.In part presented at the Seventh International Symposium on Advances in Chromatography, Las Vegas, Nevada, November 29 / December 3, 1971 and the Second International Symposium on Pyrolysis Gas Chromatography, Paris, September 28/29, 1972     

Hydrogen-bonded donor--acceptor compounds for organic ferroelectric materials

Organic ferroelectrics are multifunctional candidates for future organic electronic and optical devices. In spite of their potential, only a few organic compounds are known to exhibit a ferroelectric transition. The conventional approach to ferroelectrics, in general, relies on the use of asymmetric dipolar molecules and/or substituents. Recently, distinct design strategies have been developed using the molecular compounds of binary- or multi-components, combined with "non-covalent" forces: charge-transfer interactions and/or hydrogen bonding. This article focuses on the supramolecular systems of hydrogen-bonded acid and base molecules. Ferroelectricity and a significant dielectric response, as well as an antiferroelectric ordering induced by proton transfer, are demonstrated in the hydrogen-bonded chains composed of 2,5-dihydroxy-p-benzoquinone derivatives and nitrogen-containing aromatic bases.     

A nickel(ii)-based one-dimensional organic–inorganic halide perovskite ferroelectric with the highest Curie temperature

Organic–inorganic halide perovskites (OIHPs) are very eye-catching due to their chemical tunability and rich physical properties such as ferroelectricity, magnetism, photovoltaic properties and photoluminescence. However, no nickel-based OIHP ferroelectrics have been reported so far. Here, we designed an ABX₃ OIHP ferroelectric (3-pyrrolinium)NiCl₃, where the 3-pyrrolinium cations are located on the voids surrounded by one-dimensional chains composed of NiCl₆-face-sharing octahedra via hydrogen bonding interactions. Such a unique structure enables the (3-pyrrolinium)NiCl₃ with a high spontaneous polarization (P_s) of 5.8 μC cm⁻² and a high Curie temperature (T_c) of 428 K, realizing dramatic enhancement of 112 and 52 K compared to its isostructural (3-pyrrolinium)MCl₃ (M = Cd, Mn). To our knowledge, remarkably, (3-pyrrolinium)NiCl₃ should be the first case of nickel(ii)-based OIHP ferroelectric to date, and its T_c of 428 K (35 K above that of BaTiO₃) is the highest among all reported one-dimensional OIHP ferroelectrics. This work offers a new structural building block for enriching the family of OIHP structures and will inspire the further exploration of new nickel(ii)-based OIHP ferroelectrics.

Organic–inorganic halide perovskites (OIHPs) are very eye-catching due to their chemical tunability and rich physical properties such as ferroelectricity, magnetism, photovoltaic properties and photoluminescence.     

A multifunctional molecular ferroelectric with chiral features,a high Curie temperature,large spontaneous polarization and photoluminescence: (C9H14N)2CdBr4

Low-dimensional chiral organic–inorganic hybrid metal halides have attracted a lot of attention in recent years due to their unique intrinsic properties, including having potential applications in optoelectronic and spintronic devices. However, low-dimensional chiral molecular ferroelectrics are very rare. In this paper, we report a novel zero-dimensional molecular ferroelectric (C₉H₁₄N)₂CdBr₄ (C₉H₁₄N⁺ = protonated 3-phenylpropylamine), which has obvious dielectric and thermal anomalies and shows a high Curie temperature at 395 K. It crystallizes in the P2₁ space group at room temperature, showing a strong CD signal, large spontaneous polarization (P_s = 13.5 μC cm⁻²), and a clear ferroelectric domain. In addition, it also exhibits a flexible SHG response. The photoluminescence spectrum shows that 1 has broadband luminescence. At the same time, compound 1 has a wide band gap, which is mainly contributed to by the inorganic CdBr₄ tetrahedron. The high tunability of low-dimensional chiral molecular ferroelectrics also opens up a way to explore multifunctional chiral materials.

A novel molecular ferroelectric (C₉H₁₄N)₂CdBr₄ with high Curie temperature (T_c = 395 K), strong CD signal, large spontaneous polarization, clear ferroelectric domain and fluorescence characteristics.     

Orientational ordering of a ferroelectric liquid crystal with high spontaneous polarization

The orientational ordering of the liquid crystal, 3M2CPHOB ((2S, 3S)-3-methyl-2-chloropentanoic acid-4′,4″-hexyloxybiphenyl ester) in its smectic A and chiral smectic C phases has been studied by carbon-13 2D N.M.R. The technique used is separated local-field spectroscopy, which produces a first-order splitting for each carbon signal, from which carbon-proton dipolar constants can be determined. The order parameters for different molecular segments of the liquid crystal can then be calculated. The C-H bond order parameter at the chiral centre with a chlorine atom is unusually large, which is a strong indication of hindered rotation of the molecular segment at the chiral centre. The carbon-13 chemical shifts of 3M2CPHOB were also measured as a function of temperature, and the relation between the chemical shifts and the order parameters is discussed.     

Orientational ordering of a ferroelectric liquid crystal with high spontaneous polarization

The orientational ordering of the liquid crystal, 3M2CPHOB ((2S, 3S)-3-methyl-2-chloropentanoic acid-4',4'-hexyloxybiphenyl ester) in its smectic A and chiral smectic C phases has been studied by carbon-13 2D N.M.R. The technique used is separated local-field spectroscopy, which produces a first-order splitting for each carbon signal, from which carbon-proton dipolar constants can be determined. The order parameters for different molecular segments of the liquid crystal can then be calculated. The C-H bond order parameter at the chiral centre with a chlorine atom is unusually large, which is a strong indication of hindered rotation of the molecular segment at the chiral centre. The carbon-13 chemical shifts of 3M2CPHOB were also measured as a function of temperature, and the relation between the chemical shifts and the order parameters is discussed.     

Physics of organic ferroelectric field‐effect transistors

Most of the envisaged applications of organic electronics require a nonvolatile memory that can be programmed, erased, and read electrically. Ferroelectric field‐effect transistors (FeFET) are especially suitable due to the nondestructive read‐out and low power consumption. Here, an analytical model is presented that describes the charge transport in organic FeFETs. The model combines an empirical expression for the ferroelectric polarization with a density dependent hopping charge transport in organic semiconductors. Transfer curves can be calculated with parameters that are directly linked to the physical properties of both the comprising ferroelectric and semiconductor materials. A unipolar FeFET switches between a polarized and depolarized state, and an ambipolar FeFET switches between two stable polarized states. A good agreement between experimental and calculated current is obtained. The method is generic; any other analytical model for the polarization and charge transport can be easily implemented and can be used to identify the origin of the different transconductances reported in the literature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

A splitless Curie point pyrolysis capillary inlet system for use with the adsorption wire technique of vapour analysis

Summary A splitless Curie point pyrolysis inlet system for capillary columns has been built using conventional packed column apparatus. This has enabled the adsorption wire analysis system, for the rapid collection and direct GC analysis of vapours, to be used with capillary columns. Use of the technique for detecting traces of hydrocarbon fuels in arson investigation is described, as are problems occurring in its use.     

Defect-assisted conductivity in organic ionic plastic crystals

In order to determine the role of defects (vacancies and extended lattice defects) in the conductivity mechanism of a well studied organic ionic plastic crystal electrolyte, conductivity and mean defect volumes were measured. The ionic conductivity of the salt showed a characteristic phase dependence. Defect volumes, as measured by positron annihilation lifetime spectroscopy, showed increasing rates of expansion with increasing rotational disorder. The dependence of ionic conductivity on defect volume was observed to be phase dependent. Increases in mean defect volume size below approximately 100 cm(3) mol(-1) did not always facilitate ionic conductivity. It was shown that the material undergoes a solid-solid phase transition to the most disordered phase (a plastic crystalline phase with the highest conductivity) when the mean defect volume becomes larger than the molar volume of either the rotating anionic or cationic species. Conductivity in this phase had the strongest dependence on defect volume. Critical volumes calculated from the free volume model of Cohen and Turnbull were unrealistically large.     

Use of a replicated Latin square design in a homogeneity test for high purity organic melting point standards

The use of a replicated Latin square design for reference material homogeneity assessment is illustrated by application to a homogeneity study of eight high-purity organic materials certified for melting point. The design controlled for both a three-level location effect and a run effect. Variance components were extracted using mixed effects modelling using a restricted maximum likelihood method. An alternative classical ANOVA calculation is also given. The effect of appreciable numerical rounding by the instrument software was investigated and shown to be acceptable for the particular example. Estimation of the scale of location and run effects showed that in this example the location effect was both statistically and practically significant, while the run effect was not statistically significant at the 95% level of confidence. The design allowed unbiased estimates of between-unit variances in the presence of both interfering effects.