TY - JOUR A1 - Zhu, Shigen A1 - Schulz, Burkhard A1 - Bruma, Maria A1 - Brehmer, Ludwig T1 - Comparative study of the thermal properties of related aromatic polyhydrazides and poly(1,3,4-oxadiazole)s Y1 - 1996 UR - http://www3.interscience.wiley.com/journal/5401/home?CRETRY=1&SRETRY=0 U6 - https://doi.org/10.1002/(SICI)1099-1581(199612)7:12<879::AID-PAT600>3.0.CO;2-X SN - 1042-7147 ER - TY - JOUR A1 - Yusupov, R. G. A1 - Frübing, Peter A1 - Brehmer, Ludwig A1 - Mislavski, B. V. T1 - Langmuir Filme des Polymers "NAFION" als sensibles Element eines Feuchtesensors Y1 - 1995 ER - TY - JOUR A1 - Wüstneck, Rainer A1 - Prescher, Dietrich A1 - Katholy, Stefan A1 - Knochenhauer, Gerald A1 - Brehmer, Ludwig T1 - Surface dilatational rheological study of the trans-cis isomerisation of copolymers with trifluoromethoxy substituted metacrylate monolayers Y1 - 2000 SN - 0927-7757 ER - TY - JOUR A1 - Wong, J. E. A1 - Detert, H. A1 - Brehmer, Ludwig A1 - Schrader, Sigurd T1 - Green light-emitting devices based on soluble oligo(phenylenevinylenes) N2 - In this work, we report our investigations on the film-forming properties as well as the optical and electroluminescent characterisations of a series of lateral-substituted soluble oligo(phenylenevinylenes) of various conjugation length. Preliminary investigations show that these materials are potential candidates for use in organic light-emitting devices (OLEDs). Two types of OLEDs were fabricated: single layer (SL) and single heterostructure (SHS), with poly(p-phenylenevinylene) (PPV) as hole transporting layer. Our best results were obtained with single layer device emitting green light with a luminance of 0.18 cd m(-2) and 0.24 cd m(-2) at a driving voltage of 10 V. (c) 2004 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0169-4332 ER - TY - JOUR A1 - Wang, G. A1 - Nespurek, S. A1 - Rakusan, J. A1 - Karaskova, M. A1 - Schauer, F. A1 - Brehmer, Ludwig T1 - Polarized electrolumineseence from bilayer structures N2 - The photoalignment ability of poly[methyl(phenyl)silylene] (PMPSi) films makes it possible to use them as hole- transporting substrates for the preparation of organic oriented films. A PMPSi layer prepared by spin coating was irradiated, after drying, with linearly polarized UV light. Then, water-soluble hydroxyaluminium phthalocyaninesulfonate [Al(OH)Pc(SO3Na)(1-2)] was deposited by casting. The cell ITO/PMPSi/AI(OH)Pc(SO3Na)(1-2)/Al showed non-linear current- voltage characteristics. For applied voltages higher than 10 V, polarized electroluminescence was observed. Its spectral characteristic consisted of two peaks with maxima at about 320 and 700 nm; their polarized anisotropies R-EL = Phi(parallel to) / Phi(perpendicular to) were ca. 15 and 0.5, respectively Y1 - 2004 SN - 1022-1360 ER - TY - JOUR A1 - Stiller, Burkhard A1 - Köpnick, Thomas A1 - Muzikante, I. A1 - Neilands, O. A1 - Utinans, M. A1 - Dubrovich, O. A1 - Karageorgiev, Peter A1 - Brehmer, Ludwig T1 - Optically induced switching effect of polymer containing indandione-1,3-pyridinium betaine side chains Y1 - 1999 SN - 0378-2271 ER - TY - JOUR A1 - Stiller, Burkhard A1 - Karageorgiev, Peter A1 - Perez, E. A1 - Valez, M. A1 - Reiche, Jürgen A1 - Prescher, Dietrich A1 - Dietzel, Birgit A1 - Brehmer, Ludwig T1 - Scanning kelvin microscopy as a tool for visualisation of optically induced molecular switching in azobenzene self assembling films Y1 - 2000 SN - 0142-2421 ER - TY - JOUR A1 - Stiller, Burkhard A1 - Karageorgiev, Peter A1 - Buchsteiner, Andrea A1 - Geue, Thomas A1 - Henneberg, Oliver A1 - Brehmer, Ludwig A1 - Natansohn, Almeria A1 - Hollricher, Olga T1 - Using light as a tool : optically Induced mass transport generated in Near-Fields Y1 - 2003 SN - 0038-7355 - ER - TY - JOUR A1 - Stephan, Jörg A1 - Schrader, Sigurd A1 - Brehmer, Ludwig T1 - Monte Carlo simulations of charge transport in molecular solids : a modified Miller Abrahams type jump rate approach Y1 - 2000 ER - TY - JOUR A1 - Stephan, Jörg A1 - Liemant, Alfred A1 - Albrecht, Fred A1 - Brehmer, Ludwig T1 - Interplay of polaronic and disorder effects on electronic charge transport Y1 - 2000 ER - TY - JOUR A1 - Stephan, Jörg A1 - Brehmer, Ludwig T1 - Dynamic Monte Carlo simulation of organic molecular beam deposition: influence of growth parameters on film morphology Y1 - 2000 ER - TY - JOUR A1 - Smertenko, P. S. A1 - Dimitriev, O. P. A1 - Schrader, Sigurd A1 - Brehmer, Ludwig T1 - Doping of polyaniline by transition metal salts : current-voltage characteristics of the ITO/polymer film/metal heterostructures N2 - Films of emeraldine base of polyaniline (PAni) doped by various transition metal salts have been prepared, and current-voltage characteristics of the indium-tin oxide (ITO)/PAni film/metal electrode heterostructures were investigated. It was found that the electrical characteristics of the heterostructures are greatly affected by the dopant used and the metal electrode used. Different dopants resulted in different current anomalies with asymmetric current-voltage characteristics. Depending on the dopant used, the exponential and power law of the current behavior can be distinguished. Depending on the metal electrode used, two different regimes of current passing have been found at low applied voltages, namely, a nearly ohmic regime for the indium electrode, and a diode regime for the aluminum electrode. The diode regime was found to accompany by a positive charge accumulation in the film near the film/metal interface, which creates a built-in potential in the film. The amount of positive charges accumulated at the interface and therefore the value of the built-in potential can be reversibly increased or reduced by successive runs of the applied voltage in the forward or reverse direction, respectively. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0379-6779 ER - TY - JOUR A1 - Smela, E. A1 - Kaminorz, Yvette A1 - Inganäs, O. A1 - Brehmer, Ludwig T1 - Planar microfabricated polymer light-emitting diodes N2 - Conjugated polymers are organic semiconducting materials that can emit light. These polymers have the advantages of being light, cheap, and easy to process, and in addition the band gap can be tailored. We report the microfabrication of surface light emitting diodes (SLEDs) on silicon substrates in which the electrodes are underneath the organic electroluminescent layer. Patterned electrodes are separated by a 2500Å-thick insulating layer of silicon oxide or are interdigitated with a separation of 10 or 20 µm; the luminescent polymer is spin-coated or solvent cast on top of the electrodes. This fabrication method is completely compatible with conventional silicon processing because the polymer is deposited last and the light is emitted from the upper surface of the diodes. Despite the large spacing between electrodes, and despite the absence of an evaporated top contact, the voltages required for light emission were not much greater than those used in conventional sandwich-type structures Y1 - 1998 ER - TY - JOUR A1 - Schürmann, H. A1 - Koch, Norbert A1 - Imperia, Paolo A1 - Schrader, Sigurd A1 - Jandke, M. A1 - Strohriegl, P. A1 - Schulz, Burkhard A1 - Leising, G. A1 - Brehmer, Ludwig T1 - Ultraviolet photoelectron spectroscopic study of heterocyclic model compounds for electroluminescent devices Y1 - 1999 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Stiller, Burkhard A1 - Zetzsche, Thomas A1 - Knochenhauer, Gerald A1 - Dietel, Reinhard A1 - Brehmer, Ludwig T1 - Characterization of 2,5-di(p-tolyl-1,3,4- oxadiazole) crystals by IR-spectroscopy and atomic force microscopy Y1 - 1995 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Stiller, Burkhard A1 - Zetzsche, Thomas A1 - Knochenhauer, Gerald A1 - Dietel, Reinhard A1 - Brehmer, Ludwig T1 - Crystal structure of 2,5-Di(4- methoxycarbonyl-phenyl)-1,3,4-oxadiazole characterized by AFM and IR- spectroscopy Y1 - 1994 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Knochenhauer, Gerald A1 - Brehmer, Ludwig A1 - Janietz, Silvia T1 - Stuctures and properties of aromatic poly(1,3,4-oxadiazole)s Y1 - 1995 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Knochenhauer, Gerald A1 - Brehmer, Ludwig A1 - Janietz, Silvia T1 - Stuctures and properties of aromatic poly(1,3,4-oxadiazole)s Y1 - 1994 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Brehmer, Ludwig A1 - Knochenhauer, Gerald T1 - Supramolecular structures of aromatic 1,3,4-oxadiazole solids Y1 - 1995 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Brehmer, Ludwig A1 - Dietzel, Birgit A1 - Zetzsche, Thomas T1 - Preparation and characterization of ordered thin films based on aromatic poly(1,3,4-oxadiazole)s Y1 - 1995 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Brehmer, Ludwig T1 - Preparation and characterization of ordered thin films based on aromatic poly(1,3,4-oxadiazole)s Y1 - 1995 ER - TY - JOUR A1 - Schröter, J. A. A1 - Plehner, R. A1 - Tschierske, C. A1 - Katholy, Stefan A1 - Janietz, Dietmar A1 - Peñacorada, Florencio A1 - Brehmer, Ludwig T1 - Monolayer properties of a new family of amphiphiles with an unusual head-group topology Y1 - 1997 ER - TY - JOUR A1 - Schrader, Sigurd A1 - Vismants, Z. A1 - Dietzel, Birgit A1 - Flueraru, C. A1 - Prescher, Dietrich A1 - Reiche, Jürgen A1 - Motschmann, H. A1 - Brehmer, Ludwig T1 - Linear and nonlinear optical properties of Langmuir-Blodgett multilayers from chromophore-containing maleic acid anhydride polymers Y1 - 1999 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Zetzsche, Thomas A1 - Helms, Andreas A1 - Freydank, Anke-Christine A1 - Knochenhauer, Gerald A1 - Schulz, Burkhard A1 - Brehmer, Ludwig T1 - Organized molecular films of oxadiazole compounds formed by vacuum deposition Y1 - 1997 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Schulz, Burkhard A1 - Knochenhauer, Gerald A1 - Dietzel, Birgit A1 - Freydank, Anke-Christine A1 - Zetzsche, Thomas A1 - Brehmer, Ludwig T1 - Supramolecular structures formed from heterocyclic aromatic molecules N2 - This paper describes the formation and structure investigation of Langmuir monolayers and Langmuir-Blodgett multilayers formed from amphiphilic derivatives of 2,5-diphenyl-1,3,4-oxadiazole. The 2,5-diphenyl-1,3,4-oxadiazole group as a functional unit with interesting physical and chemical properties is maintained, while the head group, the length of the alkyl chain and the structure of the coupling unit between aromatic and aliphatic part of these linear short-chain amphiphiles is systematically varied in order to explore the influence of this change on the film forming properties and the stability of Langmuir and Langmuir-Blodgett films. Molecular mechanics simulations are shown by these systematic variations to be suitable for the prediction of optimal chemical structures allowing for a stable stratified molecular packing. The combination of a detailed structure investigation of the multilayers based on scanning force microscopy and X-ray data with molecular mechanics simulations yields an insight into the packing of the molecules and the intermolecular interactions. Y1 - 1997 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Penacorada, Florencio A1 - Zetzsche, Thomas A1 - Katholy, Stefan A1 - Brehmer, Ludwig T1 - Polyelektrolyt-Fettsäure-Multiphasen-LB-Schichten Y1 - 1995 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Penacorada, Florencio A1 - Geue, Thomas A1 - Pietsch, Ullrich A1 - Brehmer, Ludwig T1 - In-plane structure of uranylarachidate multilayers Y1 - 1995 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Penacorada, Florencio A1 - Geue, Thomas A1 - Pietsch, Ullrich A1 - Brehmer, Ludwig T1 - Monolayers and multilayers of uranyl arachidate : in-plane structure of uranyl arachidate multilayers N2 - The molecular in-plane structure of uranyl arachidate Langmuir-Blodgett (LB) films formed at different subphase pH values was analysed by means of X-ray grazing-incidence diffraction. For multilayers formed at low subphase pH a reorganisation of the arachidic acid film structure is confirmed. At appropriate subphase pH values, reorganisation of the film structure, e.g. via the formation of three-dimensional crystallites, is prevented by the presence of the uranyl ions and by the subsequent introduction of conformational disorder (gauche defects) in the alkyl chains. The observation of a macroscopic flow-induced in-plane texture in these uranyl arachidate LB films has profound implications for the design of ordered, supramolecular structures by the Langmuir-Blodgett technique. Y1 - 1997 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Knochenhauer, Gerald A1 - Dietel, Reinhard A1 - Freydank, Anke-Christine A1 - Zetzsche, Thomas A1 - Pietsch, Ullrich A1 - Brehmer, Ludwig A1 - Barberka, Thomas Andreas A1 - Geue, Thomas T1 - Structure of thermally treated oxadiazoleamide Langmuir-Blodgett films N2 - The thermal treatment of Y-type Langmuir-Blodgett (LB) films formed from the amphiphilic derivative of 2,5- diphenyl-1,3,4-oxadiazole 1 results in changes of the molecular packing. These changes have been analysed by a combination of X-ray specular reflectivity data, X-ray grazing incidence diffraction data and scanning force microscopy images, On the basis of these experimental data we have simulated possible supramolecular structures, These simulations provide insight into the intermolecular interactions giving rise to the observed structural transitions. The crystalline structure induced by thermal treatment of the LB films is characterized by a uniaxial texture, which is correlated with the dipping direction during deposition of the LB film. Y1 - 1997 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Knochenhauer, Gerald A1 - Barberka, Thomas Andreas A1 - Geue, Thomas A1 - Pietsch, Ullrich A1 - Brehmer, Ludwig A1 - Hodge, P. A1 - Tredgold, Richard H. T1 - In-plane structure of perfluorotetra decanoic acid Langmuir-Blodgett films and films formed by vacuum deposition Y1 - 1995 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Kamusewitz, Helmut A1 - Keller, Manuela A1 - Brehmer, Ludwig A1 - Peñacorada, Florencio T1 - Study of gas transport through composite membranes with a stabilised Langmuir-Blodgett skin layer N2 - The Langmuir-Blodgett (LB-) technique is used to deposit molecular reinforced separation layers on porous polymer substrates resulting in composite membranes for gas separation. The adsorption of a polycation to the arachidic acid Langmuir layer and the subsequent transfer of the highly ordered and stabilised monolayer onto a polypropylene membrane (Cellgard 2400) yields a laminated separation layer combining the advantageous high degree of order of fatty acid films and the stability of thin polymeric films. X-ray reflectivity data of these films confirm the transfer of the assembled polymer layer together with the fatty acid monolayer and the formation of ordered Y-type LB-films. SFM pictures show a dense film without pinholes completely covering the porous support. Gas permeation measurements are used to study the transport process of different gases through the composite membrane. Y1 - 1995 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Janietz, Dietmar A1 - Barberka, Thomas Andreas A1 - Hofmann, Dieter A1 - Brehmer, Ludwig T1 - Comprehensive structure investigation of Langmuir-Blodgett films of disc-shaped molecules N2 - The structure of mono- and multilayers of amphiphilic disc-shaped pentaynes wa inbestigated by Brewsterangle microscopy, X-ray specular reflection and grazing incidence diffraction (GID). X-ray specular reflection experiments confirm the "edge on" arrangement of the molecular discs. The molecular modelling of the Langmuir-Blodgett (LB)- multilayers predicts a columnar in-plane packing of the molecules. A GID experiment with monochromatic synchrotron radiation was used to verify the predicted multilayer structure on molecular level, while the Brewsterangle microscopy gave a deeper insight in the monolayer in-plane structure on micron scale. Y1 - 1995 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Freydank, A. A1 - Dietzel, Birgit A1 - Katholy, Stefan A1 - Knochenhauer, Gerald A1 - Zetzsche, Thomas A1 - Schulz, Burkhard A1 - Brehmer, Ludwig T1 - Komplexe Strukturanalytik von Oxadiazol-Mono- und Multischichten Y1 - 1995 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Dietzel, Birgit A1 - Freydank, Anke-Christine A1 - Geue, Thomas A1 - Pietsch, Ullrich A1 - Brehmer, Ludwig T1 - Lateral structure of thermally treated oxadiazole Langmuir-Blodgett films Y1 - 1995 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Dietel, Reinhard A1 - Lemmetyinen, Helge A1 - Janietz, Dietmar A1 - Lemmetyinen, Helge A1 - Brehmer, Ludwig T1 - Edge-on Langmuir-Blodgett multilayers derived from disc-shaped multiyne mesogens N2 - Langmuir-Blodgett(LB) multilayers were prepared from disc-shaped multiyne mesogens based on amphiphilic alkyl pentakis(aryl-ethynyl)benzene ethers. The two compounds used are characterized by five hydrophobic flexible chains and one hydrophilic substituent at the terminal position of the alkoxy chain. The LB films were analysed by X-ray scattering and spectroscopic measurements. An edge-on arrangement of the two discotic pentaalkynes within Y-type bilayers with a different packing density proved to be possible for the LB films of both compounds. Y1 - 1992 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Brehmer, Ludwig T1 - Einfluss des Transferverhältnisses auf die Monoschichtsymmetrie in Y-Typ Langmuir-Blodgett-Schichten Y1 - 1995 ER - TY - JOUR A1 - Reiche, Jürgen A1 - Barberka, Thomas Andreas A1 - Janietz, Dietmar A1 - Hofmann, Dieter A1 - Pietsch, Ullrich A1 - Brehmer, Ludwig T1 - X-ray structure investigation and computer modelling of Langmuir-Blodgett films formed from disc-shaped pentaalkines Y1 - 1994 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Yusupov, R. G. A1 - Milaski, B. A1 - Frübing, Peter A1 - Brehmer, Ludwig T1 - Elektrische Eigenschaften von polyionischen LB-Filmen Y1 - 1995 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Souto, Jorge A1 - de Saja, J. A. A1 - Brehmer, Ludwig T1 - Brewster angle microscopy and surface potential measurements of Langmuir-Blodgett films of zinc tri(tert-butyl)- 4-sulphophthalocyanine N2 - The formation of a Langmuir monolayer of an amphiphilic derivative of zinc phthalocyanine (Na[(ZnPcSO3)-S-t]) has been studied by means of surface potential technique and Brewster angle microscopy. The experiments were undertaken in order to understand the behaviour of this monolayer with a well-defined surface pressure isotherm. The floating film is described as a truly monomolecular layer formed by very rigid islands in which the phthalocyanine units tend to take on a preferential orientation with their planes perpendicular to the air-water interface, for high values of the surface pressure. (c) 2004 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0169-4332 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Reiche, Jürgen A1 - Zetzsche, Thomas A1 - Dietel, Reinhard A1 - Brehmer, Ludwig A1 - Saja, Jose-Antonio de T1 - Stabilisation of fatty acid mono- and multilayers by simultaneous polyelectrolyte complexation and salt formation with cadmium ions N2 - The complexation of highly ordered fatty acid monolayers with polyelectrolytes is expected to yield well- ordered Langmuir films suitable for the formation of Langmuir-Blodgett multilayers with improved long-term stability. Studies of the surface pressure-area isotherms and of the surface potential kinetics yield detailed information regarding the influence of these polymeric counterions on the monolayer properties. The injection of bivalent metal salts into the subphase after the complexation was used to improve the order and stability of the mono- and multilayers. The corresponding Langmuir-Blodgett films were investigated by means of X-ray reflectivity measurements and scanning force microscopy. The polyion complex multilayers show a strongly increased mechanical stability compared with films of fatty acid salts formed with bivalent metal ions. These structures are expected to be suitable as ultrathin separation layer for gas separation or ultrafiltration membranes. Y1 - 1997 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Reiche, Jürgen A1 - Katholy, Stefan A1 - Brehmer, Ludwig A1 - Rodriguez-Mendez, Maria-Luisa T1 - Monolayers and multilayers of uranyl arachidate : 1. study of the interaction of dissolved uranyl ions with arachidic acid Langmuir monolayers N2 - Langmuir monolayers of arachidic acid have been prepared on a subphase containing uranyl ions (O-U-O)ý+. The interaction between the uranyl ions and the monolayer of arachidic acid has been studied by means of surface pressure and surface potential isotherms and Brewster angle microscopy at different pH values (ranging from 1.5 to 8). A similar systematic study has been carried out in the presence of Cdý+ ions for comparison purposes. The surface pressure and surface potential isotherms demonstrate that the acid to salt conversion of arachidic acid in the presence of uranyl ions occurs at lower bulk pH values (pH=3.5) as compared with other bivalent metal counterions such as Cdý+. Changes in the surface morphology of the monolayer induced by the interaction with uranyl- and cadmium ions are analyzed and the correlation between the surface potential change and the morphology of the films is discussed. Y1 - 1995 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Reiche, Jürgen A1 - Dietel, Reinhard A1 - Zetzsche, Thomas A1 - Stiller, Burkhard A1 - Knobloch, Harald A1 - Brehmer, Ludwig T1 - Monolayers and multilayers of uranyl arachidate : 2. Influence of the subphase pH on the structure and stability of Langmuir-Blodgett films N2 - In this second paper we describe the comprehensive structure investigations on multilayers of uranyl arachidate formed by Langmuir-Blodgett deposition from subphases of different pH on solid substrates by means of a combination of infrared spectroscopy, X-ray specular reflection, ellipsometry, and scanning force microscopy, The structure of these multilayers and their stability are obviously influenced by the subphase pH. The pH range of the acid to salt conversion determined for the Langmuir films is confirmed by the infrared spectroscopic data of the multilayers. While arachidic acid films, deposited from an uranyl acetate subphase of low pH, are found to have strongly distorted rough surface, the films of uranyl structure, The influence of the counterions on the alkyl chain conformation, chain packing, reorganization probability, and stability of the multilayer is discussed. Y1 - 1996 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Dietel, Reinhard A1 - Reiche, Jürgen A1 - Zetzsche, Thomas A1 - Knobloch, Harald A1 - Katholy, Stefan A1 - Brehmer, Ludwig T1 - Studium des Einflusses von Uranyl-Gegenionen auf die Struktur von Langmuir- und Langmuir-Blodgett Filmen der Arachinsäure Y1 - 1995 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Angelova, Angelina A1 - Kamusewitz, Helmut A1 - Reiche, Jürgen A1 - Brehmer, Ludwig T1 - Scanning Force Microscopy and Wetting study of the Surface Modification of a Polypropylene Mambrane by Means of Langmuir-Blodgett Film Deposition N2 - Polypropylene membranes with deposited ultrathin "siin" layers are attractive for separation and cleaning of gaseous mixtures. In the present study, the surface morphology and wetting hysteresis of composite membranes consisting of a microporous polypropylene support and Langmuir-Blodgett ("skin") films, are investigated. The effect of the interlayer molecular interactions and the substrate features on the integrity and homogeneity of the "skin" layers is examined. Langmuir-Blodgett films of arachidic acid and cadmium and calcium arachidate are characterized both on smooth silicon and on porous polypropylene supports. Contact angle measurements and scanning force microscopy (SFM) are applied for investigations of the membrane surface modification upon transfer of a different number of monolayers. It was found that the contact angle hysteresis of the bare membrane decreases after the LB-deposition of close-packed monolayers. Smoothing of the membrane surface is also evidenced by the SFM images, on different length scales, confirming a good coverage of the membrane pores. Y1 - 1995 ER - TY - JOUR A1 - Papra, Alex A1 - Penacorada, Florencio A1 - Reiche, Jürgen A1 - Katholy, Stefan A1 - Brehmer, Ludwig A1 - Hicke, Hans-Georg T1 - Structure and Stability of Langmuir Monolayers and Langmuir-Blodgett Films of Bisaroyl Azide Bolaamphiphiles N2 - Langmuir-Blodgett films of bolaamphiphiles with reactive head groups can be used for the surface modification of composite membranes for gas separation processes. The scope of our investigations was to get a detailed insight in the monolayer behaviour and LB film structure of previously synthesized bisaroyl azide bolaamphiphiles. The layers have been analyses by means of surface potential measurements and Brewster angle microscopy. Furthermore parameters for a successful LB Film deposition were found. As expected for a molecule with two hydrophilic ends the transfer ratio on upstroke was close to one and on downstroke no transfer occurred. The multilayer structure was analysed by scanning force microscopy and X-ray reflectivity measurements. The SFM images revealed a periodic in plane structure on molecular level. Based on a combination of the X-ray data with results of other methods two possible models of the multilayer structure are presented Y1 - 1997 ER - TY - JOUR A1 - Muzikante, I. A1 - Fonavs, E. A1 - Tokmakov, A. A1 - Cepite, D. A1 - Stiller, Burkhard A1 - Brehmer, Ludwig A1 - Neilands, O. T1 - Optical and electrical properties of oriented thin films of oligomer containing betaine-type moiety in side chain N2 - Non-linear optical and electrical properties of polymer films obtained by dipole orientation of active units are reported. Novel polar oligomer with N-(indan-1,3-dion-2-yl)pyridinium betaine (IPB) as a side group is studied. Orientation of polar groups in oligomer thin films causes an increase of the photo-induced change of surface potential on irradiation in the region of photo-induced electron transfer (PIET) where the IPB group exhibits a reversible change of the value and sign of the dipole moment. At longer wavelengths, the value of the surface potential of the oligomer may be determined by transport of photo-generated charge carriers Y1 - 2005 SN - 0370-1972 ER - TY - JOUR A1 - Metzger, Robert M. A1 - Chen, Bo A1 - Höpfner, Ulf A1 - Lakshmikantham, M. V. A1 - Vuillaume, Dominique A1 - Kawai, Tsuyoshi A1 - Wu, Xiangli A1 - Tachibana, Hiroaki A1 - Hughes, Terry A1 - Sakurai, Hiromi A1 - Baldwin, Jeffrey W. A1 - Hosch, Christina A1 - Cava, Michael P. A1 - Brehmer, Ludwig A1 - Ashwell, Geoffrey J. T1 - Unimolecular electrical rectification in Hexadecylquinolinium Tricyanoquinodimethanide Y1 - 1997 ER - TY - JOUR A1 - Liemant, Alfred A1 - Brehmer, Ludwig T1 - A mean field approximation for hopping transport in disordered materials Y1 - 1996 ER - TY - JOUR A1 - Knochenhauer, Gerald A1 - Reiche, Jürgen A1 - Barberka, Thomas Andreas A1 - Woolley, Martin A1 - Tredgold, Richard H. A1 - Hodge, P. A1 - Brehmer, Ludwig T1 - Do perfluorianted chains always have to be twisted? N2 - Short perfluorinated cabon chains do not take on helical structure when they are closely packed Y1 - 1995 ER - TY - JOUR A1 - Knochenhauer, Gerald A1 - Penacorada, Florencio A1 - Reiche, Jürgen A1 - Brehmer, Ludwig A1 - Tredgold, Richard H. A1 - Barberka, Thomas Andreas T1 - Multilayers of perfluorinated fatty acids N2 - We have formed Y layers of perfluorododecanoic acid CF3(CF2)10COOH by thermal evaporation in vacuo and of perfluorotetradecanoic acid CF3(CF2)12COOH by thermal evaporation and by the Langmuir-Blodgett (LB) technique. We have obtained the bilayer spacing of both these materials by X-ray diffraction and have also studied the in-plane structure of these materials by means of grazing incidence diffraction (GID). Computer modelling was used to interpret the results obtained. For the perfluorododecanoic acid, we find two stable untwisted phases at 25°C and a combination of these two predicts both the Bragg peaks arising from the layer structure and the GID results. Our experimental results show that the perfluorotetradecanoic acid exists in the generally accepted helical structure. Computer modelling leads to the conclusion that closely packed perfluorinated chains with 12 or less carbon atoms should exist in an untwisted state while molecules having more than 12 carbon atoms show the onset of the helical conformation. Y1 - 1999 ER -