Electronic Structure Of Poly Research Articles

Redox properties of poly(tetrathiafulvalenes)

The electronic structure of poly(tetrathiafulvalenes), PTTF, was determined using the Hückel theory. The calculated redox potentials of the polymer and the gap energy of 2.2 eV are in agreement with experimental values obtained by charge-discharge measurements. To determine the absorption spectra and the gap energy the photoacoustic technique was used.

Electronic structure of poly(p‐phenylene sulfide)

AbstractThe electronic structure of poly(p‐phenylene sulfide) (PPS) was studied through steady state photocurrent spectra and temperature dependence of dark conductivity for undoped film, by changes in the in situ optical absorption and ESR spectra under photoirradiation, and optical absorption spectra for doped film. The charge carriers in the undoped state are electronic since the photoconductivity is large and the kink point in the temperature dependence of dark conductivity is higher than the glass transition temperature. A sharp peak near the absorption edge in the photocurrent spectrum of undoped PPS is caused by the diffusion of photocarriers in a sheet with high surface recombination under conditions of low applied field. The in situ optical absorption and ESR spectra of SO3‐doped PPS were similar to those of di‐p‐tolyl sulfide (a monomer unit of PPS) and the formation of sulfur‐centered radical cations was suggested rather than bipolaron states. The stable conduction of SO3‐doped PPS after exposure to atmosphere was analyzed by the classical Lorentz model and the existence of nearly free carriers within subchains was suggested. Their conductivity and mobility were estimated to be 2 S/cm and 3.6 cm2/Vs, respectively. Inter‐chain conduction appears to be very low.

Electronic structure of poly(ether—ether—ketone), PEEK

The electronic structure of poly(ether—ether—ketone) (PEEK) is investigated by combining X-ray and ultraviolet photoelectron spectroscopy data with the results of theoretical calculations. XPS core level spectra are related to the charge distribution on the chain, and shake-up satellites are analyzed in terms of electron interaction between the phenyl rings. The UPS spectra are interpreted from the theoretical densities of valence states calculated by the valence effective Hamiltonian (VEH) method. The results show that the electronic structure of PEEK is basically identical to that of a short-chain model molecule, indicating that the ground state of the polymer remains localized, with no long-range electronic interaction along the chain.

Electronic structure of poly(tetrafluoroethylene) studied by UPS, VUV absorption, and band calculations

The electronic structure of poly(tetrafluoroethylene) (PTFE) was studied by UPS, VUV absorption, and ab-initio MO calculations. The UPS spectra give a photoemission threshold energy of 10.6eV, with deeper valence band features consistent with the reported XPS and the oligomer vapour UPS spectra. The UPS spectra are also consistent with the density of states derived from the calculated band structure, which indicates that the uppermost part of the valence band is formed from the C and F 2p orbitals with C-C bonding and C-F antibonding combinations. The VUV absorption spectrum shows an intense peak at 7.7eV, which most probably corresponds to the valence excitation from the top of the valence band to the bottom of the conduction band. With these data, the structure of the occupied and vacant states are deduced.

Conformation and electronic structure of poly(3,4-diisopropylidenecyclobutene), a cross-conjugated conductive polymer

It has been reported recently that the title polymer, 1, synthesized by a novel olefin-metathesis route, can be oxidatively doped to yield materials with moderate conductivities. Theoretical studies reveal that, due to steric crowding, polymer 1 cannot achieve a planar, fully-conjugated structure in either its undoped or doped states. Rather, the structure consists of essentially orthogonal tetramethylhexatriene units. Such a structure is incompatible with conventional conduction mechanisms involving polarons or bipolarons. It is proposed that, instead, conduction involves intra- and/or inter-chain charge transfer.

Defects in the electronic structure of poly (p-phenylene vinylene): Electronic spectra, electrochemical behavior, and molecular orbital calculations

The electronic spectrum of thin films of poly(p-phenylene vinylene) (PPV) in an insulating neutral form exhibits three absorption bands with maxima at 6.12, 5.06, and 3.08 eV. The first two maxima are related to localized molecular states and the broad band at 3.08 eV is described in terms of a vibrationally coupled exciton model. Upon electrochemical doping of PPV, two additional absorption bands appear at 0.80 and 2.10 eV which are associated with a dication whose charge is spread over a few monomer units. Thin films of PPV can be electrochemically converted from the oxidized (conducting) form to the neutral (insulating) form repeatedly in LiAsF6/propylene carbonate solution without evidence of decomposition. The E0 measured using cyclic voltammetry is 3.85 V vs a Li/Li+ reference electrode; however, the observed optically active defects occur in a region of higher potential.

Optical spectra and electronic structure of poly(3-methylthiophene)

Optical spectra of conducting polymer, poly(3-methylthiophene), (P3MT), were investigated for wide spectral range of 30 – 45000 cm −1. Strong electronic transition, which were not found in the previous studies on lightly doped film, was found in the far-i.r. reflectance of the heavily doped film. It is a metallic type reflectance with nearly zero transition energy, and implies that the free carrier is formed in the heavily doped film. In addition the pinning mode of the bipolaron oscillation was found rather strongly at 720 cm −1, which is close to the value of Hayes (1985). The midgap transitions, which have been attributed to the characteristic band of bipolaron, were found at 3200 and 13000 cm −1 consistent with the results of Chung (1984) and Harbeke (1985).

Electronic structure of poly(dichlorophosphazene)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectronic structure of poly(dichlorophosphazene)Kazuyoshi Tanaka, Shoji Yamashita, and Tokio YamabeCite this: Macromolecules 1986, 19, 7, 2062–2064Publication Date (Print):July 1, 1986Publication History Published online1 May 2002Published inissue 1 July 1986https://doi.org/10.1021/ma00161a046RIGHTS & PERMISSIONSArticle Views71Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (367 KB) Get e-Alerts Get e-Alerts

Defect states in poly(p-phenylene methine) and similar materials

The electronic structure of poly(p-phenylene methine), PPM, obtained using a Huckel model with a bond-order bond-length relationship is degenerate and capable of supporting soliton defects, PPM thus being the parent of a class of π-conjugated polymer characterised by a repeat unit consisting of a ring sequence symmetrically interconnected by an odd-alternant group; an unusual structural relaxation about the polaron defect for PPM is described.

The electronic structure of poly(p-xylylene)

Ultraviolet photoemission spectra of poly(p-xylylene) films are measured and compared with those of gas-phase and thin-film p-xylene. Comparison of the spectra with CNDO/S3 molecular orbital calculations of the density of valence electron states reveals that photoinduced π-electron molecular-ion states in poly(p-xylylene) are localized on individual phenyl moieties.