Ferroelectric metal-organic framework with a high dielectric constant

Hydrothermal reaction of (l)-N-(4'-cyanobenzy)-(S)-proline with CdCl2 as a Lewis acid catalyst and NaN3 gives colorless block compound 1, in which 1 displays a complicated 3D framework. Ferroelectric and dielectric property measurements reveal that 1 exhibits physical properties comparable to that of a typical ferroelectric compound with a dipole relaxation process and a dielectric constant of ca. 38.6 that makes it, by definition, a high dielectric material.     

Ferroelectric metal-organic coordination polymer with a high dielectric constant

Two homochiral MOFs, (CBQ)CuI3(CN)3Br (1) and (CBC)CuI2.5(CN)2Br1.5 (2), were prepared by the solvothermal reaction of CuCN with N-4-cyanobenzyl quinidinium bromide (CBQ-Br) and N-4-cyanobenzylcinchonidinium bromide (CBC-Br). 1 and 2 are typical ferroelectric compounds while may have dipolar relaxation ferroelectrics and a high dielectric constant (epsilon o = 119.3).     

Homochiral 1D zinc-quitenine coordination polymer with a high dielectric constant

Heat treatment of a solution of MeOH and water containing the quitenine ligand HQA [HQA = 6-methoxyl-(8S,9R)-cinchonan-9-ol-3-carboxylic acid] and ZnCl2 at 70 degrees C to give the one-dimensional (1D) chain coordination polymer {(HQA)(ZnCl2)(2.5H2O)}n (1). The local coordination geometry around the zinc center in 1 displays a slightly distorted tetrahedron, with the HQA ligand adopting a zwitterionic moiety similar to that found in natural amino acids. Measurements on a powdered sample of 1 reveal a strong second-harmonic-generation response of ca. 20 times larger than that for KDP (KH2PO4). Notably, measurements on the dielectric properties of 1 showed that the 1D chain coordination polymer exhibited a dipolar chain relaxation process and a high dielectric constant (epsilon0= 37.3).     

Implications of a high dielectric constant in proteins

Solvation of protein surface charges plays an important role for the protonation states of titratable surface groups and is routinely incorporated in low dielectric protein models using surface accessible areas. For many-body protein simulations, however, such dielectric boundary methods are rarely tractable and a greater level of simplification is desirable. In this work, we scrutinize how charges on a high dielectric surface are affected by the nonpolar interior core of the protein. A simple dielectric model, which models the interior as a low dielectric sphere, combined with Monte Carlo simulations, shows that for small, hydrophilic proteins the effect of the low dielectric interior is largely negligible and that the protein (and solution) can be approximated with a uniform high dielectric constant equal to that of the solvent. This is verified by estimates of titration curves and acidity constants for four different proteins (BPTI, calbindin D(9k), ribonuclease A, and turkey ovomucoid third domain) that all correlate well with experimental data. Furthermore, the high dielectric approximation follows as a natural consequence of the multipole expansion of the potential due to embedded protein charges in the presence of the low dielectric core region.     

The formation of percolative composites with a high dielectric constant and high conductivity

The dielectric constant and electrical conductivity of a composite of two insulators, poly(1,1-difluoroethylene) (yellow) and K(2) CO(3) (white), increased dramatically near the percolation threshold?f(c) (f=concentration of K(2) CO(3) ). This intriguing phenomenon can be interpreted in terms of interface percolation caused by the formation of chemically activated interfaces.     

Photosensitive fluorinated polyimides with a low dielectric constant based on reaction development patterning

The fluorinated polyimide PI(6FDA/HFBAPP) was prepared by the reaction of 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 2,2‐bis[4‐(4‐aminophenoxy)phenyl]hexafluoropropane (HFBAPP) in 1‐methyl‐2‐pyrrolidone/toluene. A multiblock copolyimide with both fluorinated and rigid‐rod segments, PI(6FDA/HFBAPP)(BPDA/2‐DMB), was prepared by the addition of a second dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), and a second diamine, 2,2′‐dimethylbenzidine (2‐DMB), to the polyimide main chain. The potential lithographic performance of photosensitive polyimides composed of nonphotosensitive fluorine‐containing polyimides and photosensitive diazonaphthoquinone (DNQ) was studied on the basis of a new imaging principle recently proposed by our laboratory, that is, reaction development patterning. Neat PI(6FDA/HFBAPP) showed a low dielectric constant (?) of 2.41 and a low dissipation factor (tan δ) of 0.0027 at 20 GHz, and a 10‐μm resolution of the fluorinated polyimide/DNQ system was demonstrated with reactive development with a solution including ethanolamine after ultraviolet exposure. Although slight changes in the dielectric properties were observed in the presence of DNQ residues, these values (? = 2.63 and tan δ = 0.0033 at 20 GHz) were low enough for use in microelectronic applications. However, PI(6FDA/HFBAPP)(BPDA/2‐DMB), having a lower coefficient of thermal expansion (CTE; 33 ppm/°C) than PI(6FDA/HFBAPP) (49 ppm/°C), exhibited good positive photosensitivity, whereas the relatively low‐CTE multiblock copolyimide displayed a much higher ? value (3.48 at 1 MHz) than the highly fluorinated polyimide (2.88 at 1 MHz). A film consisting of PI(6FDA/HFBAPP)(BPDA/2‐DMB) and the remaining DNQ derivatives showed a CTE value comparable to that of the neat polyimide film. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 861–871, 2003     

The dielectric constant and oscillometric measurement

Summary New evidence is given that the characteristic conductance and susceptance curves of high frequency measurements, expressed as a function of the log of the electrolyte concentration, depend only on the physical parameters of the measuring cell, and the Debye effect plays only an insignificant role.

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Zusammenfassung Wie neuerlich gezeigt wurde, sind die Konduktanz- und Susceptibilitäts. kurven bei Hochfrequenzmessungen, ausgedrückt als Funktion des Logarithmus der Elektrolytkonzentration nur von den physikalischen Parametern der Meßzelle abhängig. Der Debye-Effekt spielt keine signifikante Rolle.

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Résumé On donne une nouvelle preuve que les courbes caractéristiques de la conductance et de la susceptance des mesures en haute fréquence, exprimées en fonction du log de la concentration de l'électrolyte, ne dépendent que des paramètres physiques de la cellule de mesure, et que l'effet Debye ne joue qu'un rôle minime.

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Presented at the Symposium on Analytical Chemistry, Graz, 29th September–1st October 1965.     

Some polymers of high dielectric constant

A class of highly conjugated macromolecules exhibiting extraordinarily high effective dielectric constants (DK = 50–900) is described. These polymers are of the polyacene radical quinone type, are highly purified, and exhibit electronic semiconduction. The dielectric constant varies only slightly with pressure (up to 20 Kbar), but strongly with frequency (300–300,000 cps) and moderately with temperature and field strength. The latter effect of field strength on the effective dielectric constant (and on the conductivity) required the development of special measurement techniques which are described. The unusual dielectric behavior can be accounted for assuming the presence of what amounts to a thermally generated plasma of electrons and holes, each locally mobile on extended regions of associated π-orbitals on the molecules. The postulated resulting “hyperelectronic” polarization of the locally mobile charges in external fields fits the observed high magnitude of the polarizability, as well as its field, frequency, and temperature dependence.     

Polymer design for thermally stable polyimides with low dielectric constant

We successfully prepared a series of thermally stable polyimides (PIs) with low dielectric constant (k) by introducing bulky diphenyl fluorenylidene moieties in backbone. The lowest k was found to be 2.77 among non-fluorinated PIs and 2.35 among fluorinated ones. In order to prove the lowest limit of k in PIs, we prepared soluble and thermally stable polyarylenes (PArs) without polar imide linkage with the same aromatic moieties by coupling polymerization. The lowest k was 2.7 without fluorine (F) and 2.2 with F atom, which showed also promising for low k materials. From these results, PIs we prepared were estimated to the lowest k values among PIs. On the basis of statistics on these results, we could express contour lines of k as a function of imide concentration and F content with high correlation factor (r= 0.96) in PIs and PArs.     

Homochiral laminar europium metal-organic framework with unprecedented giant dielectric anisotropy

Hydrothermal (deuteratothermal) reaction of L-ethyl lactate (Lig-Et) with Eu(ClO(4))(3)6 H(2)O gives colorless block crystals of [Eu(Lig)(2)(X(2)O)(2)][ClO(4)] (1, X=H; 2, X=D) both of which possess a two-dimensional laminar homochiral framework. Single-crystal dielectric measurements reveal that 1 and 2 display a giant dielectric anisotropy approximately exceeding 100 and large isotopic effect with about 54 % enhancement along the a axis. Their ferroelectric features further confirm this respect. Crystal parameters: 1, C(6)H(14)ClO(12)Eu, M(r)=465.58, monoclinic, C(2), a=8.6786(6), b=8.3965(6), c=10.2153(7) A, beta=92.040(1) degrees , V=743.92(9) A(3), Z=2, rho(calcd)=2.079 Mg m(-3), R(1)=0.0508, wR(2)=0.1239, mu=4.448 mm(-1), S=1.043; Flack=0.04(5). 2: C(6)H(10)D(4)ClO(12)Eu, M(r)=469.61, monoclinic, C(2), a=8.689(2), b=8.410(2), c=10.224(3) A, beta=92.057(4) degrees , V=746.7(3) A(3), Z=2, rho(calcd)=2.089 Mg m(-3), R(1)=0.0465, wR(2)=0.1150, mu=4.432 mm(-1), S=1.058; Flack=0.02(5).     

Anisotropy of the dielectric constant of polyacetylene

The dielectric constant ? of polyacetylene films oriented by rolling was measured. The variation of ? and also that of the proton nuclear magnetic resonance line shape indicate that rolling partially isomerizes cis(CH)_x. For oriented trans(CH)_x we find ?_∥ = 5.7 and ?_? = 4.0 in the plane of the film. A calculation based on bond polarizabilities leads to qualitative agreement with experiment.     

Nearly constant dielectric loss behavior in ionomers

The electrical conductivity of a series of ionomers has been characterized by measuring the electrical conductivity in a relatively broad range of frequencies and temperatures. At low frequencies, the conductivity of the ionomers exhibits a universal Jonscher power law (JPL), and at higher frequencies a nearly constant loss (NCL) behavior. The NCL for the ionomers is qualitatively similar to that observed for other inorganic ionic conductors. However, the magnitude of NCL for ionomers is lower than that observed for inorganic ionic conductors. The analysis of the conductivity master curves suggests that the conduction mechanism, which includes both the NCL and the JPL behaviors, is governed by ion hopping of the mobile ions.     

Theory of the dielectric constant of ice

The first result of this paper is to show that the Onsager—Slater theory of the dielectric constant is consistent for some reasoable model of ice in the limit of no intrinsic defects. Accordingly, a model is presented, called the unit model, which has unit cells with no dipole moments for which the Onsager—Slater theory is exact. The second result of this paper is to show that the unit model is physically and chemically realistic. Bjerrum defects are introduced into the model and the relation between the dielectric constant and the Bjerrum defect charge found by Onsager and Dupuis for a less realistic model continues to hold and is satisfied by the experimental values. In a simple point charge approximation the charge distribution determined by the model requirements and the experimentally determined Bjerrum fault charge are found and seem reasonble. Higher order multipole interaction energies are consistent with eviations from pure 1/T dependence of the dielectric constant of real ice with intrinsic defects, can be derived in the context of the unit model. This formula interpolates between the Onsager—Slater formula in the limit of no intrinsic defects and the Kirkwood—Frohlich formula in the limit of many intrinsic defects. For the concentration of defects in real ice the interpolation formula is practically the same as the Onsager—Slater formula and differs from the Kirkwood—Frohlich formula by a factor of nearly $\text{3}\text{2}$.     

On the dielectric constant of nonpolar fluids

Referring to a recent paper in this journal of Stell and Rushbrooke the deviation from the Clausius-Mossotti relation for the static dielectric constant of a nonpolar fluid is discussed. In particular a number of coefficients in the dielectric virial expansion have been evaluated for a hard-sphere system.     

On the dielectric constant of nonpolar fluids

We discuss the recent work of Wertheim on the dielectric constant of nonpolar fluids, and also present some new calculations on the Kirkwood-Yvon theory. These serve to emphasise the prime importance of the state dependence of the effective polarisability in interpreting deviations from the Clausius-Mossotti theory for real dense fluids.     

Low dielectric constant polyimide nanomats by electrospinning

The proper combination of material (i.e. fluorinated polyimides) and processing technique (electrospinning) could lead to the formation of polyimides with low dielectric constant, high thermo‐oxidative stability and glass transition temperature, and high hydrophobicity. The polyimides in this work were based on 4, 4‐bis [3′‐trifluoromethyl‐4′ (4′‐amino benzoxy) benzyl] biphenyl (Q) and various fluorinated and non‐fluorinated dianhydrides namely benzene‐1,2,4,5‐tetracarboxylic dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride, benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride, and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Processing of the polyimides was carried out in poly(amic acid) stage by two different methods—electrospinning and solution casting for comparison purposes. The processing of polyimides by electrospinning led to enhancement in mechanical properties (dianhydride‐structure dependent) and hydrophobicity without sacrificing thermo‐oxidative stability and glass transition temperatures significantly. Also, low dielectric constants (as low as 1.43) could be attained by suitable combination of dianhydride (6FDA) with 4, 4‐bis [3′‐trifluoromethyl‐4′ (4′‐amino benzoxy) benzyl] biphenyl diamine. Copyright © 2011 John Wiley & Sons, Ltd.     

The dielectric constant of lamellar semicrystalline polymers

The problem of representing the dielectric constant of semicrystalline polymers in terms of the dielectric constants and volume fractions of the constitutent crystalline and amorphous phases is considered. For locally lamellar morphology, bounds based on uniform electric and displacement fields are derived. The equations also include the degree of crystal orientation as a parameter. For unoriented polymers the bounds are considerably tighter than the Hashin–Shtrikman bounds, the latter being the best possible without knowledge of phase geometries. The bounds presented here are sufficiently tight to represent the dielectric constant with practical accuracy for a number of examples of semicrystalline polymers. A treatment is also given of the dielectric constant where the lamellar morphology is further specified as being organized into spherulite-like structures. These bounds are somewhat tighter than the lamellar bounds.     

Novel soluble thermally stable silane-containing aromatic polyimides with reduced dielectric constant

Bis(p-aminophenoxy)diphenylsilane (BPS), bis(m-aminophenoxy)diphenylsilane (BMS) and bis(5-amino-1-naphthoxy)diphenylsilane (BAS) as three silane-diamines were prepared by the reactions of 4-aminophenol, 3-aminophenol, and 5-amino-1-naphthol respectively, with dichlorodiphenylsilane in the presence of triethylamine. The related silane-containing polyimides were prepared by two-step polycondensation reactions of these diamines with three different aromatic dianhydrides. All the polymers were characterized and their physical and thermal properties were studied. The polymers showed high thermal stability while their solubility was greatly increased in polar aprotic solvents. Wide angle X-ray diffraction showed that all the polyimides were almost amorphous. Also their dielectric constants were decreased due to the incorporation of softening and low-polarizing siloxane units into the polymer backbone.     

The first ionothermal synthesis of a 3D ferroelectric metal-organic framework with colossal dielectric constant

A novel 3D (4,6)-connected topological architecture, obtained under ionothermal conditions by using 1-ethyl-3-methyl imidazolium bromide ([EMI]Br) as solvent and structure-directing agent, presents a non-centrosymmetric polar packing arrangement showing an interesting ferroelectric property.