The electronic structure of tris(8-hydroxyquinoline) aluminum (Alq3) has been studied in the pristine molecular solid state as well as upon interaction (doping) with potassium and lithium. We discuss the results of a joint theoretical and experimental investigation, based on a combination of x-ray and ultraviolet photoelectron spectroscopies with quantum-chemical calculations at the density functional theory level. Upon doping, each electron transferred from an alkali metal atom is stored on one of the three ligands of the Alq3 molecule, resulting in a new spectral feature (peak) in the valence band that evolves uniformly when going from a doping level of one to three metal atoms per Alq3 molecule.

Aluminum is widely used as cathode material in organic electroactive devices. In this work the interface formation between the electroluminescent material p-sexiphenyl(6P) and this metal was investigated with photoelectron spectroscopy. In strong contrast to the findings for the interaction of polyenes and oligothiophenes with Al, where covalent bonds are formed, we obtain clear evidence for physisorption of Al on 6P. This is supported by quantum chemical calculations, carried out on model systems.

The microscopic morphology of thin films of block copolymers is investigated with Atomic Force Microscopy (AFM). The block copolymers consist of a conjugated polyparaphenylene segment associated to either a polystyrene or a polymethyl methacrylate thermoplastic sequence. Formation of phase-segregated microdomains is observed on the nanometer scale. The AFM images are interpreted in terms of molecular packing with the help of molecular dynamics calculations.

Self-assembly of block copolymers is attractive for nanodevice fabrication because the association of different polymers by covalent bonding and the interplay between the sequences allows one to generate a variety of structures with well-defined shapes. We present a straightforward approach to generate self-organized organic semiconducting nanostructures. This approach is based on the spontaneous molecular organization of block copolymers containing one fully conjugated segment associated with a nonconjugated sequence. Such systems show high local contrast in their properties and are of interest for applications in nanoscale patterning for quantum confinement of light emission or fabrication of nanowire networks.

Chapter 6 Geometric and Electronic Structure and Optical Response of Oligo- and Polythiophenes: Relation to Their Use in Electro-optic and Photonic Devices J. Cornil, J. CornilSearch for more papers by this authorD. Beljonne, D. BeljonneSearch for more papers by this authorV. Parente, V. ParenteSearch for more papers by this authorR. Lazzaroni, R. LazzaroniSearch for more papers by this authorJ. L. Brédas, J. L. BrédasSearch for more papers by this author J. Cornil, J. CornilSearch for more papers by this authorD. Beljonne, D. BeljonneSearch for more papers by this authorV. Parente, V. ParenteSearch for more papers by this authorR. Lazzaroni, R. LazzaroniSearch for more papers by this authorJ. L. Brédas, J. L. BrédasSearch for more papers by this author Book Editor(s):Dr. Denis Fichou, Dr. Denis Fichou Laboratoire des Matériaux Moléculaires, C.N.R.S., 2, rue Henry-Dunant, F-94320 Thiais, FranceSearch for more papers by this author First published: 26 November 1998 https://doi.org/10.1002/9783527611713.ch6Citations: 2 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains sections titled: Introduction Theoretical Methodology Electronic and Linear Optical properties of Neutral Oligothiophenes Electronic and Linear Optical Properties of Charged Oligothiphenes Characterization of Metal/polymer Interfaces Nonlinear Optical Properties of Neutral Oligothiophenes Synopsis Citing Literature Handbook of Oligo- and Polythiophenes RelatedInformation

The interface between aluminum and electroluminescent sexiphenyl (6P) is investigated by means of photoelectron spectroscopy together with quantum mechanical calculations. X-ray and ultraviolet photoelectron spectroscopy are used to reveal that the interaction of aluminum-often used as the electron-injecting electrode in light-emitting diodes-on a 6P surface is of the van der Waals type, i.e., the metal atoms physisorb on the organic compound. In addition, it is calculated that bond formation between Al atoms and phenylene oligomers is not energetically favored.

We investigate theoretically the geometric structure and vibrational properties of complexes of polyenes with aluminum atoms that constitute model systems for the species formed at the interface between aluminum and polyacetylene. The calculations are performed with two quantum-mechanical techniques: ab initio Hartree-Fock and density functional theory in the local spin density approximation. These methods are first applied to a polyene molecule, all-trans octatetraene, and the calculated vibrational spectra are compared to existing experimental and theoretical data. The molecule is then made to interact with two aluminum atoms in various configurations. Since the metal atoms form covalent bonds with carbon atoms in the central part of octatetraene, strong geometric modifications occur along the conjugated system, which in turn deeply affect the vibrational spectra. These results allow us to derive the expected infrared signature of the chemical species present at the interface.

Atomic Force Microscopy (AFM) and related techniques are used to investigate the morphology of diblock copolymers. We focus on compounds containing a conjugated segment, polyparaphenylene, associated to a polymethylmethacrylate or a polystyrene block. The influence of the presence of the conjugated segment on the microdomain morphology is analyzed as a function of chain composition. Separate microdomains are observed on the surface of thin films by means of phase-detection imaging tapping-mode AFM. Their shape and size are interpreted in terms of molecular aggregation, with the help of molecular dynamics calculations.

We investigate theoretically the chemical structure and vibrational properties of the interface between aluminum and polythiophene, taken as a prototype conjugated polymer, considering both the deposition of the metal on a polymer substrate and the adsorption of the polymer on the metal surface. We perform quantum-mechanical calculations to determine the geometric and electronic structure and vibrational frequencies in a series of molecular model systems for the Al-polythiophene interfaces.

The interaction of water with poly-p-phenylene vinylene is investigated theoretically by means of quantum-chemical calculations on molecular model systems. Water is found to form van der Waals complexes characterized by hydrogen-like bonds with the protons and/or the π system of the PPV chain. The formation of such complexes can lead to significant conformational changes which, in turn, affect the electronic properties of the conjugated polymer.

The copper/polymer interface has been studied by VUV photoemission for poly-3-hexylthiophene (P3HT) as a model of conjugated polymers, at low metal coverage.

The exposure of poly(p‐phenylenevinylene), PPV, to air affects its performance in polymer‐based light‐emitting devices. An investigation is described in which exposure to air is demonstrated to give rise to reversible affects associated with the absorption of water vapor, leading to determinal changes in the outer electronic structure (see also the cover of this issue). In particular the resulting increase in torsion angle is shown to lead to a reduction in conjugation. A method of preparing clean PPV films is proposed.

We present a theoretical study on aluminium triisopropoxide (Al((OPr)-Pr-1)(3)) using both empirical (Molecular Mechanics, MM, with Dreiding II force field) and quantum-chemical (Austin Model 1, AM1, semiempirical Hartree-Fock) techniques. We determine the most stable geometries for both the tetramer and trimer of aluminium triisopropoxide as well as the thermodynamic characteristics of the equilibrium existing between these two aggregated structures. The theoretical results are compared to experimental data from X-ray diffraction and Al-27 NMR measurements. For the tetramer, it appears that the optimal equilibrium geometries are in good agreement with the experimental X-ray diffraction geometry; another geometry is also obtained with both theoretical approaches, which is slightly less stable but of higher symmetry. On the basis of the most stable configurations for the tetramer and trimer aggregates, the variation of free enthalpy (Delta G) between the two aggregated structures has been estimated. The evolution of the theoretical Delta G values indicates a displacement of equilibrium towards the trimer species with temperature, in good agreement with experimental H-1 and Al-27 NMR data. Moreover, the AMI heats of formation show a gain of 33.9 kcal/mol due to the aggregation of four Al((OPr)-Pr-1)(3) instead of three, and thus a better stability of the tetramer. The molecular geometries being well described by the theoretical methods used in this study, we also present a model for the ring-opening polymerization complexes of epsilon-caprolactone and lactides.

The chemical structure and vibrational properties of the interface between aluminum and polyacetylene are studied theoretically with a quantum-chemical approach. A density-functional-based technique is used to perform calculations on model systems for the interface, consisting of a polyene oligomer interacting with two aluminum atoms. The bonding configuration of the aluminum atoms on the molecule is investigated and the vibrational frequencies of the aluminum/polyene complex are determined. The analysis of the data provides the vibrational signature which is expected for the chemical species generated during the initial stages of the interface formation.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSelective Localization of Carbon Black in Immiscible Polymer Blends: A Useful Tool To Design Electrical Conductive CompositesF. Gubbels, R. Jerome, Ph. Teyssie, E. Vanlathem, R. Deltour, A. Calderone, V. Parente, and J. L. BredasCite this: Macromolecules 1994, 27, 7, 1972–1974Publication Date (Print):March 1, 1994Publication History Published online1 May 2002Published inissue 1 March 1994https://pubs.acs.org/doi/10.1021/ma00085a049https://doi.org/10.1021/ma00085a049research-articleACS PublicationsRequest reuse permissionsArticle Views5636Altmetric-Citations374LEARN 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 InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

This work deals with the microscopic description of the electronic and geometric structures at the interface between hydrocarbon polymers, such as polyethylene or polystyrene, and a carbon surface, i.e., graphite or carbon black. In order to understand the nature of the local interactions at the interfaces, we performed theoretical calculations, based on both quantum-mechanical ab initio techniques and empirical molecular mechanics techniques. The interfaces between polyethylene and graphite and between polystyrene and graphite are modeled by considering the alkane/benzene and ethylbenzene/benzene complexes, respectively.

This work deals with the quantum-mechanical modeling of the interactions occurring at the molecular level during the formation of the interface between aluminum and polythiophene. Density-functinal theory calculations are performed on a molecular model system consisting of a thiophene molecule surrounded by one or two aluminum atoms. The geometric structure of the organometalic complex is fully optimized and the possibilities of aluimum bonding to various sites of the molecules are evaluated. The evolution of the charge density distribution upon metal bonding is followed using a Mulliken population analysis.