Polyacene Quinone Radical Polymers Research Articles

Synthesis and characterization of three different structures of polyacene quinone radical polymers

Three types of polyacene quinone radical (PAQR) polymers were synthesized by the step-growth polymerization of naphthalene, anthracene, or anthraquinone reacting with pyromellitic dianhydride via solution polymerization under a temperature gradient. Zinc chloride was used as the catalyst, and nitrobenzene was the solvent. The different structures of PAQR polymers were analyzed by infrared, X-ray diffraction, and scanning electron microscopy. The thermal properties of PAQR polymers were described by thermal gravimetric analysis, and the electrical performances were investigated by a precision LCR meter and a digital high insulation meter.

Preparation and Characterization of PAQR Polymers by Different Methods

Polyacene quinone radical (PAQR) polymers were formed by different methods, using anthraquinone and pyromellitic anhydride with aromatic acids through the solvothermal method and solid phase melted polymerization. High temperature was also applied to increase the polymerization degrees and exclude the oligomer that can not be excluded during the purification process. The different structures of PAQR polymers were analyzed by XRD, Raman, XPS, and Element Analyzer. The properties of PAQR polymers were investigated through TG and VNA.

Ab initio study of electronic structure, quantum transport and optical absorption properties of polyacene quinone radical polymers

Semiempirical quantum mechanical calculations have been implemented to study the molecular structure, electronic structure, optical properties of polyacene quinone radical polymers, and the quantum transport properties are also been calculated through combination of the numerical atomic orbitals basis set method based on density functional theory with the non-equilibrium Green's function formalism. The polyacene quinone radical polymers exhibit similar elastic modulus to the carbon nanotubes. The electronic molecular orbitals and energy bands of polyacene quinone radical polymers show insulator features, with the great conjugated bonds formed in polymer molecules resulting in extreme high polarization and dielectric constants, and the Fermi energy and band-gaps of ultraviolet range are static with the variation of polymerization degree. The aluminum electrodes with crystallographic (001) surfaces have been used in the electronic transport calculations, which indicate the quantum conductance spectrum changes with the varied strain and polymerization degree, however appears no explicit change, representing large open-gap feature of insulators. Ultraviolet-visible absorption spectra show a few characteristic peaks, the positions and number of which varying with polymerization degree, predicting that polyacene quinone radical polymers, as high dielectric functional materials, could be applied to ultraviolet optoelectronic nanoscale quantum devices.

Synthesis of polyacene quinone radical polymers with controllable conductivity and their smart electrorheological behavior

Polyacene quinone radical (PAQR) polymers were synthesized by the step-growth condensation of aromatic hydrocarbon derivatives reacting with pyromellitic anhydride via a solvothermal method. The morphology and structures of PAQRs with varied polymerization processes were confirmed by the analysis of X-ray, IR, SEM and TG measurement. The effects of different aromatic hydrocarbons on the synthesis and morphology of PAQR polymers were investigated and then utilized as an electrorheological (ER) material by dispersion in silicone oil. The ER performances are investigated as a function of electric field strength by using a rheometer and the relationship between the conductivity and electrorheological (ER) properties of different polyacene quinone radical (PAQR) polymers were discussed.

Dielectric Studies on the Heterogeneity and Interfacial Property of Composites Made of Polyacene Quinone Radical Polymers and Sulfonated Polyurethanes

Sulfonated polyurethane (PUI, matrix) is synthesized and composited with polyacene quinone radical polymers (PAQRs, filler). The polarization mechanism of these polymers and composites were investigated in terms of their frequency, temperature, and filler-concentration-dependent dielectric properties. We found that PUI/PAQR composites have a high permittivity, which is attributed to the filler-matrix interfacial polarization and the contact effect. The PAQR-concentration-dependent permittivity of different PUI/PAQR composites reveals a percolation threshold at 20-30 wt % with scaling exponents that indicate the intercluster polarization. The frequency dependence of dielectric response is well-fitted by using the Debye and Cole-Cole functions on the basis of the structural diagrams and equivalent circuit, leading to a detailed evaluation on heterogeneous structures of different PUI/PAQR composites.

Synthesis of Polyacene Quinone Radical Polymers by Solvothermal Method

In this paper Polyacene quinone radical (PAQR) polymers were synthesized by the step-growth condensation of aromatic hydrocarbon derivatives reacting with pyromellitic anhydirde via a solvothermal method at 180°C for 2 h, using zinc chloride as catalyst and cyclohexane as solvent. The effects of solvents and different aromatic hydrocarbons on the synthesis and morphology of PAQR polymers were investigated.

Synthesis and characterization of polyacene quinone radical polymers with high-dielectric constant

Polyacene quinone radical polymers (PAQRs) and their hydroxyl- or alkoxyl-modified derivates (HO-PAQR and RO-PAQR) were synthesized through the solid-state heating, the solution polymerization, and the improved process (pre-polymerization before solid-state heating). PAQRs synthesized by the improved process provided the higher yields than those from the other two methods. The high-dielectric constants were achieved for the PAQRs from the solid state and the improved process, due to the high polarization resulted from the existence of large amount of polar domains, which were the aggregation of the conjugated ladder-structured macromolecules with extended regions of associated π-orbital. The HO-PAQRs or RO-PAQRs showed good blending or solving features in polymer or solvent, but they were of low dielectric constants for the groups of hydroxyl and alkoxyl destroyed the planar conjugation of the associated π-orbital, and provided the steric hindrance to the formation of regular stacks of the conjugated macromolecules, which could produce huge polarization. The molecular and the aggregated structures of PAQRs with varied chemical modifications and from varied polymerization processes were confirmed by the analysis of X-ray, IR, TG, TEM and the dielectric measurement.

Electrical properties of polymer composties: conducting polymer-polyacene quinone radical polymer

Unique electrical properties are observed in conducting polymer such as poly(3-alkylthiophene) containing various types of polyacene quinone radical polymers (PAQR) such as PMA+Py. Electrical conductivity and its temperature dependence are strongly dependent on concentration of PAQR. Dependences of dielectric properties of the polymer composite on concentration of PAQR and temperature are also anomalous. The results are discussed in terms of electronic band schemes of of both polymers.

Effect of temperature and high pressure on conductive behaviour of polyacene quinone radical polymers

We measured the d.c. conductivity of two polymers of polyacene quinone radical type as a function of pressure at various temperatures and found that there is a kink at about 2.5 kbar on plots of log conductivity versus the square root of applied pressures in range from 0.6 to 10 kbar, and that d.c. conductivity-temperature curves, even at higher temperature region (300–400 K) also obey the Mott's T 1 4 -law. In the present paper, we have given the possible interpretation of these experimental results.

Synthesis and conductivity of poly acene quinone radical polymers

AbstractPolymers with conductivities from 8.6 × 100 to 7.3 × 10−6 (ω cm)−1 at 2–12 kbar were prepared by zinc‐chloride‐catalyzed condensation of polycyclic aromatic hydrocarbons, heterocycles, and quinones with pyromellitic dianhydride, tetrabromophthalic anhydride, and tetrachlorophthalic anhydride at 450°C. These materials are stable in air and exhibit strong electroactive character without addition of oxidizing or reducing agents (dopants).

The electrical properties of amorphous polymers described by a modified variable-range hopping model

The d.c. conductivity σ dc and the thermopower S of a number of polyacene quinone radical polymers obey the relationship σ dc = σ o exp (− T o / T) 1 3 and S/T = a+bT − 1 3 , typical for two-dimensional variable-range hopping. The results can be explained by Mott's model modified, however, by allowing for a linearly varying density of states near the Fermi level, and by taking into account the form of the wave function of the localized states. Special attention is paid to the prefactor σ o which contains important hopping parameters, such as a frequency factor ν o, usually assumed to be not higher than a typical phonon frequency (∼ 10 13 s −1). The original calculation of Miller and Abrahams (MA) of the hopping rate, however, gives ν o values ranging from 10 16 to 10 21 s −1. For the PAQR polymers reasonable estimates of the parameters are obtained when using MA expressions adapted for two-dimensional systems.

IV. Two-dimensional variable-range hopping in planar conjugated macromolecules

Abstract Electrical conductivity, thermopower and Hall effect measurements have been made on a series of polyacene quinone radical (PAQR) polymers as a function of temperature. The PAQR polymers, prepared by condensing pyrene with three different acidic compounds, are highty conjugated and show fairly high conductivities (in the range 10−4-10−3 Ω−1 cm−1 at room temperature). The thermopower is positive and increases slightly with increasing temperature. The Hall coefficient, measured on one sample, is negative and decreases with temperature; the Hall mobility is less activated than the conductivity and is of the order of 3 × 10−2 cm2 V−1 s−1 at room temperature. In order to alter the electrical properties by doping, the PAQR polymers were treated with iodine. This results in an increase of the conductivity, a sign reversal of the thermopower and a lowering of the Hall mobility. The conductivity and thermopower data seem to be explained in their general features by the two-dimensional variable-range hoppin...

The charge storage and other electrical properties of a series of polyacene quinone radical polymers

A series of polyacene quinone radical polymers were made. The chemical analysis showed that the severe reaction conditions favored the Scholl (elimination of H2 and H2O) over the Friedel–Crafts reaction. Electron paramagnetic resonance spectra confirmed the presence of a biradical. Conductivity measurements in the ohmic and space charge limited regions showed that large π systems existed and that carrier traps were shallow. The π system structure and absence of quinone structure was confirmed by ir spectrometry which also showed the optical absorption edge to be 0.8 eV. Charge was injected into the polymers forming electrets and thermally stimulated current emission spectra confirmed a shallow trap depth (∼0.4 eV). It is postulated that thermal excitation to a triplet state produces the biradical and conduction is by hopping between adjacent π systems and charge storage is associated with the extensive π systems.

Hyperelectronic polarizability and electronic conduction in conjugated macromolecules

Abstract Two different types of conjugation are postulated and the concept is used to account for the high conductivity of charge transfer complexes and the high dielectric constant of polyacene-quinone radical polymers.

Hyperelectronic polarization in macromolecular solids

AbstractHyperelectronic polarization may be viewed as the electrical polarization in external fields due to the pliant interaction with the charge pairs of excitons, in which the charges are molecularly separated and range over molecularly limited domains. It is particularly pronounced in molecular solids composed of long polymeric molecules having extensive regions of electronic orbital delocalization. Hyperelectronic polarization is regarded as the principal contributor to the high polarizabilities of the following five macromolecular solids: four polyacene quinone radical polymers formed by condensation of aromatic hydrocarbon derivatives with aromatic acids and poly(Cu(II)‐N,N′‐ dimethyl rebeanate). The first four polymers at 100 hz had dielectric constants of 1800–2400, decreasing to about 58–100 at 100,000 hz, with relaxation times of 10−3 to 10−4 sec. A sixth polymer, a Schiff‐base condensate of 1,4‐napthaquinone and p‐toluene diisocyanate, however, showed little hyperelectronic polarization, displaying a dielectric constant of 10, constant over 100–100,000 hz. By simple arguments it is shown that the relaxation times and the frequency response of conduction are consonant with the proposed model of charges roaming over long molecular domains (up to 4000 A.) but restricted by molecular boundaries.

Carriers and unpaired spins in some organic semiconductors

AbstractSemiconduction and electron spin resonance studies on a number of conjugated polymers representative of the polyacetylenes, the polybenzimidazoles, and the polyacene quinone radical polymers were made. Observed resistivities ranged from 270 to 1016 ohm‐cm. at room temperature. These and the spin concentrations, the relaxation times, and the energies of activation of conductance and spin concentration were found to be functions of the molecular structure. It was considered impressive evidence that impurity effects on the electronic properties of molecular solids are far less than those commonly observed with the covalently bonded semiconductors such as Ge and Si, for example. A detailed analysis was made of the carrier and free radical formation and life‐times in these ekaconjugated molecular solids using a simple model.