| 1. |
- Dannetun, Per, et al.
(author)
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Reactions of low work function metals Na, Al, and Ca on α,ω-€diphenyltetradecaheptaene. Implications for metal/polymer interfaces
- 1994
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In: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 100:9, s. 6765-6771
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Journal article (peer-reviewed)abstract
- The interactions between different low work function metals aluminium,calcium and sodium, and α,ω‐diphenyltetradecaheptaene, a model molecule for certain conjugated polymers, have been investigated using both x‐ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The spectra are interpreted with the help of the results of quantum chemical calculations performed within the local spin density (LSD) approximation methodology. The metals are found to interact with the conjugated system in very different ways. Aluminium forms a covalent bond, which strongly modifies the π‐electronic structure of the conjugated molecule, while both the sodium and the calcium atoms act as doping agents, inducing new states in the otherwise forbidden bandgap. These new gap states can be viewed as a soliton–antisoliton pair for the Na/DP7 and a bipolaronic‐like defect for Ca/DP7.
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| 2. |
- Dannetun, Per, et al.
(author)
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Proceedings of the International Conference on Science and Technology of Synthetic Metals The chemical and electronic structure of the interface between aluminum and conjugated polymers or molecules
- 1993
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 55:1, s. 212-217
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Journal article (peer-reviewed)abstract
- The interaction between aluminum and α-ω-diphenyltetradecaheptaenee (DP7), α-sexithienyl (6T), and poly(p-phenylenevinylene) (PPV), respectively have been studied using both X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS). The UPS valence band spectra, are interpreted with the help of quantum chemical calculations based upon Modified Neglect of Diatomic Overlap (MNDO), Valence Effective Hamitonian (VEH) and ab initio Hartree-Fock methods. DP7 is a model molecule for polyacetylene, while 6T is a model molecule (an oligomer) of polythiophene. The results indicate that aluminum reacts strongly with the surfaces of all of the materials studied. The π-electronic structure of each material was strongly modified. Furthermore, aluminum reacts preferentially with the polyene partof DP7, with the vinylene part of PPV, and with the α-carbons of the thiophene nits of 6T.
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| 3. |
- Dannetun, Per, et al.
(author)
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The chemical and electronic structure of the interface between aluminum and polythiophene semiconductors
- 1993
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In: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 99:1, s. 664-672
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Journal article (peer-reviewed)abstract
- We have investigated the chemical nature and the electronic structure of the interface between a low work function metal,aluminum, and a conjugated polymersemiconductor, polythiophene. We have studied the initial stages of the interface formation by depositing the metal onto the surface of a polymer film. Charge transfer processes between the metal and the polymer are analyzed using core‐level x‐ray photoelectron spectroscopy (XPS); the evolution upon metallization of the valence electronic levels directly related to the polymerelectronic structure is followed with ultraviolet photoelectron spectroscopy (UPS). With these techniques, we investigate the deposition of aluminum on two polythiophene systems (i) the alkyl‐substituted poly‐3‐octylthiophene and (ii) the α‐sexithiophene oligomer. The experimental data are compared to the results of a recent quantum chemical study on model systems consisting of thiophene oligomers (up to sexithiophene) interacting with a few Al atoms. The interaction of polythiophene with Al atoms is found to modify dramatically the structure of the conjugated backbone, as strong carbon–aluminum bonds are formed in the α positions of the thiophene rings. A large charge transfer takes place from the Al atoms to the polymer chain, and the upper π levels of the polymer are strongly affected. The metallization is contrasted to the doping of conjugated polymers with alkali metals
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| 4. |
- Lögdlund, Michael, et al.
(author)
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A photoelectron spectroscopy study of the charge-induced π-electronic structural changes in α.ω.-diphenyltetradecaheptaene, a model molecule for polyacetylene
- 1993
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 57:2, s. 4722-4727
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Journal article (peer-reviewed)abstract
- The π€-electronic structural changes in diphenylpolyene, α.ω.-diphenyltetradecaheptaene, or DP7, have been studied upon gradually doping with sodium Xu using X-ray and Ultraviolet Photoelectron Spectroscopy, XPS and UPS. The spectra are interpreted with the help of the results from Austin Model 1 (AM1) and Valence Effective Hamiltonian (VEH) quantum chemical calculations. The results of the doping with sodium can be discussed in terms of two confined solitons on the polyene part of the molecule, which results in two new energy levels in the originally forbidden energy gap.
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| 5. |
- Lögdlund, Michael, et al.
(author)
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Experimental and Theoretical Studies of the Interaction of Metals with Polymer Surfaces : A Case Study of the Use of a Model Molecular System to Study the Nature of Charge Storage in Short Polyenes
- 1994
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In: Frontiers of Polymers and Advanced Materials. - Boston, MA : Springer-Verlag New York. - 9781461360407 - 9781461524472 ; , s. 369-382
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Book chapter (peer-reviewed)abstract
- The electronic and geometric changes in polyenes induced by doping with sodium have been studied using X-ray and Ultraviolet Photoeclectron Spectroscopy, and quantum chemical calculations. The molecular geometry changes induced by doping have been studied using the semiempirical Austin Model 1 method, the results of which has served as input parameters for Valence Effective Hamiltonian band structure calculations, which are compared with the experimental density-of-states data. The molecules studied are members of a series of diphenylpolyenes with 4, 5, 6 ir 7 C=C double bonds in the polyene part of the molecule, i.e., the series DPx, with x = 4, 5, 6 or 7. Since the frontier orbitals of the diphenylpolyenes are localized mostly on the polyene chain portion of the molecule, there is a high degree of separations in energy of the phenyl and polyene parts of the π-system. Hence, many chemical and electronic properties of diphenylpolyenes are similar to those of (at least short chain) trans-polyacerylene. The present doping results indicate the charge is stored in short polyenes in the form of two confined solitons per molecule.
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| 6. |
- Lögdlund, Michael, et al.
(author)
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Soliton pair charge storage in doped polyene molecules : Evidence from photoelectron spectroscopy studies
- 1993
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 70:7, s. 970-973
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Journal article (peer-reviewed)abstract
- The π-electronic structural changes in a polyene molecule containing seven double bonds, α,ω-diphenyltetradecaheptaene (DP7), have been studied upon gradually doping with sodium, using x-ray and ultraviolet photoelectron spectroscopies. The spectra are interpreted with the help of detailed quantum chemical calculations. Analysis of the evolution of the XPS and UPS spectra as a function of doping with sodium indicates that the extra charges are stored in the form of two charged solitons on the polyene part of the molecules, which results in two new energy levels in the originally forbidden energy gap.
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| 7. |
- Dannetun, Per, et al.
(author)
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New Results on Metal-Polymer Interfaces
- 1993
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In: Molecular Crystals and Liquid Crystals. - : Taylor & Francis. - 1542-1406 .- 1563-5287. ; 228:1, s. 43-48
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Journal article (peer-reviewed)abstract
- New results on studies of the early stages of formation of the aluminum-poly(p-phenylenevinylene) interface are presented.
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| 8. |
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| 9. |
- Fredriksson, C., et al.
(author)
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Theoretical studies of the aluminum/poly(p-phenylene vinylene) interface
- 1993
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 57:2, s. 4632-4637
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Journal article (peer-reviewed)abstract
- A molecular quantum chemical approach is used to study the aluminum on PPV (Poly(p-Phenylene Vinylene)) interface. We focus on modifications to the chemical and electronic structure of the polymer upon interaction with a submonolayer of aluminum. A model system, trans-stilbene, is taken to investigate the nature of the Al-PPV bonding. Energetically favorable conformations are then used as prototypes to study the evolution of the electronic structure as modified by the reaction with aluminum. Results at the ab initio Hartree-Fock level indicates that Al atoms react with the vinylene linkage rather than the phenyl groups at early stages of interface formation.
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| 10. |
- Fredriksson, C., et al.
(author)
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Theoretical studies of the aluminum/trans-polyacetylene interface : Calculations of model systems and comparison to experiment
- 1993
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 57:2-3, s. 4590-4595
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Journal article (peer-reviewed)abstract
- The interaction between Al atoms and trans-polyacetylene has been studied quantum chemically at the ab initio Hartree-Fock level using oligomeric model systems. Investigations of the Al-polyacetylene bonding and modifications to the chemical and electronic structure of model systems for polyacetylene upon interaction with Al atoms are reported. The density-of-states is calculated for a polyene chain interacting with a pair of Al atoms. The results are discussed in relation to photoelectron spectra taken during Al deposition on an oligomeric model for polyacetylene (a diphenylpolyene with 7 C=C bonds in the polyene segment).
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