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 - Reiche, Jürgen A1 - Freydank, Anke-Christine A1 - Helms, Andreas A1 - Geue, Thomas A1 - Schulz, Burkhard A1 - Brehmer, Ludwig A1 - Stiller, Burkhard A1 - Knochenhauer, Gerald T1 - Vacuum deposition films of oxadiazole compounds : formation and structure investigation N2 - The search for alternative routes of organic thin film formation is stimulated by the outstanding properties of these films in such fields as nonlinear optics, photonic data processing and molecular electronics. The formation of highly ordered multilayer structures by thermal vacuum deposition (VD) of organic compounds is an essential step toward the application of supramolecular organic architectures in technical systems. The VD of an amphiphilic substituted 2,5- diphenylene-1,3,4-oxadiazole 1 onto silicon substrates at defined temperature was used for the formation of ultrathin films. The structural data obtained for the VD-films of oxadiazole 1 by means of X-ray reflectivity, X-ray grazing incidence diffraction and atomic force microscopy (AFM) investigations indicate the formation of well ordered oxadiazole multilayers. The structure of the VD-multilayers is compared with that of Langmuir-Blodgett (LB) films and thermally treated LB-multilayers prepared from the same compound. Y1 - 1999 ER - TY - JOUR A1 - Akpo, Claudia A1 - Weber, Edwin A1 - Reiche, Jürgen T1 - Synthesis, Langmuir and Langmuir-Blodgett film behaviour of new dendritic amphiphiles JF - New journal of chemistry N2 - New amphiphilic compounds 1-9 that feature a construction with dendronized hydrophilic and hydrophobic segment groups connected to a specific aromatic or aliphatic spacer unit have been synthesized, following a modular building block strategy. The hydrophilic dendrons are typically branched elements with peripheral carboxylic groups, unlike the hydrophobic dendrons that contain peripheral alkyl chains as part of respective amide functions. The hydrophilic dendrons are in different generations of branching, while the hydrophobic dendrons are all in the first generation of branching (three terminal branching), but differ in the length of the alkyl chains, thus giving rise to designed structure and amphiphilic properties in the new compounds. The resulting surfactants are capable of forming well-defined Langmuir films of remarkable stability when spread from a solution onto an aqueous subphase. Nevertheless, specific packing behaviour and orientation of the amphiphilic molecules were found, depending on the molecular structure, as determined using analysis of the surface pressure-area (pi-A) isotherms. Langmuir-Blodgett transfer of the first monolayer from a pure water subphase to a clean silicon wafer proved possible for the amphiphiles of peripheral alkyl chain length C-12, while the amphiphiles with the longer alkyl chains failed, possibly due to the more rigid monolayers they form, impeding the transfer. Y1 - 2006 U6 - https://doi.org/10.1039/b609645j SN - 1144-0546 SN - 1369-9261 VL - 30 SP - 1820 EP - 1833 PB - RSC CY - Cambridge ER - TY - JOUR A1 - Wüstneck, Rainer A1 - Reiche, Jürgen A1 - Förster, Stephan T1 - Surface dilational behavior of docosanic acid monolayers spread on the surface of drops of polymer solutions N2 - The pendant drop technique was used to determine p/A isotherms of docosanic acid spread on the drop surface of an aqueous polymer solution. Two water soluble polymers were used, poly(dimethyl-diallyl-ammoniumchloride) and sodium poly(styrene sulfonate-b-ethylethylene). By fast changes of the drop volume, the monolayers were compressed and dilated. The stress relaxation was monitored and surface rheological dilation parameters were obtained. It is shown that the fatty acid monolayer can be mechanically stabilized by both interacting anionic and cationic polymers. In the case of the anionic polymer, the interaction becomes more pronounced in the presence of salts in the subphase (counterions). Brewster angle microscopy shows that the typical tilt-orientation of crystalline domains of the fatty acid monolayers transforms into a more uniform and fluid-like structure caused by the polymer/monolayer interaction. The surface rheological behavior is dramatically influenced by the polymer binding. The interaction results in surface dilational viscoelastic properties and show that there is a strong resistance against expansion of the complex fatty acid/polymer layer. 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 - Janietz, Dietmar A1 - Möbius, Dietmar A1 - Festag, R. A1 - Wendorff, Joachim Heinz A1 - Ahuja, Rajeev C. A1 - Reiche, Jürgen T1 - Supramolecular organization of amphiphilic discotic mesogens Y1 - 1994 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 - 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 - Peñacorada, Florencio A1 - Souto, Jorge A1 - Katholy, Stefan A1 - Saja, José-Antonio de A1 - Reiche, Jürgen T1 - Structure of Langmuir monolayers of substituted phthalocyanines N2 - Langmuir floating layers of two phthalocyanine derivatives, ytterbium bisphthalocyanine and tetra-tert-butyl nickel phthalocyanine, were investigated by means of compression isotherms, surface potential kinetics and Brewster angle microscopy (BAM) in order to study the influence of peripheral substituents on the structure and stability of these films and on their suitability for a subsequent transfer onto solid substrates. Specific substitutions that may lead to amphiphilic molecular units seem to play a key role in the development of well organised thin films prepared with this technique. Y1 - 1998 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 - 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 - Souto, Jorge A1 - Rodriguez-Mendez, Maria-Luisa A1 - Penacorada, Florencio A1 - Reiche, Jürgen T1 - Small angle x-ray reflectivity study of Langmuir-Blodgett films of a peripherally substituted zinc phthalocyanine N2 - Langmuir-Blodgett films of zinc 11,18,25-tri(tert-butyl)-4-sulfo-phthalocyanine (ZNPctSO3Na) have been deposited onto hydrophilic and hydrophobic silicon wafers. Y-type films were formed on both types of substrate, and the transfer ratio was very close to unity. The organization of the films on the molecular level was probed by X-ray specular reflectivity. Y1 - 1997 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 - 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 - Janietz, Dietmar A1 - Hofmann, Dieter A1 - Reiche, Jürgen T1 - Reply to comment on "Molecular organization of amphiphilic disc-shaped penta-alkynes in LB mono- and multilayers" N2 - The model for the Langmuir-Blodgett (LB) film structure of amphiphilic disc-shaped penta-alkynes is refined. It is shown that LB experiments reported in a comment on one of our papers do not contradict the molecular organization within the LB films of the penta-alkynes we proposed. Y1 - 1995 ER - TY - JOUR A1 - Koetz, Joachim A1 - Brühl, Iris A1 - Kosmella, Sabine A1 - Reiche, Jürgen A1 - Tiersch, Brigitte T1 - Polyelectrolyte Complex Formation in Lamellar Liquid Crystalline Systems N2 - The influence of polyelectrolytes on structure formation in liquid crystalline Na-dodecylsulfate/decanol/water systems was investigated by means of small angle X-ray diffraction, rheology, NMR spectroscopy, and microscopy. By adding Na-polyacrylate (PAA) into the mesophase, the one-phase region is left and phenomena of phase separation into a solvent-rich and a polymer/surfactantrich phase occurs. By incoporating an anionic and cationic polyelectrolyte step by step the tendency of phase separation is increased drastically. The self-organization process can be regulated directly by varying the water content of the system. However, at a water content of 30% the properties of the resulting liquid crystal were changed drastically. X-ray diffraction shows a multitude of Bragg peaks, NMR shows a peak-splitting, and rheology shows a change from non-Newtonian to Newtonian-flow behavior. On the basis of the experimental results an ordered multilayer associate structure can be assumed. Y1 - 1997 ER - TY - JOUR A1 - Jutila, Arimati A1 - Janietz, Dietmar A1 - Reiche, Jürgen A1 - Lemmetyinen, Helge T1 - Photophysical investigation of Langmuir-Blodgett films of amphiphilic discotic penta-alkynes N2 - Amphiphilic discotic pentakis (arylethynyl) benzene compounds 1 and 2 containing an enlarged aromatic core functioning as a chromophoric p-electron system were studied with regard to their photophysical properties within Langmuir-Blodgett (LB) films. The results obtained from steady-state absorption as well as fluorescence excitation and emission measurements will be discussed with regard to interchromophoric interactions in the LB films. Time-resolved fluorescence inves6igations revealed the formation of a ground-state complex as well as excimer formation. Thermal treatment causes irreversible destruction of the LB film structure of the discotic amphiphiles. Within droplets the reorganization of the original nematic-discotic (ND) mesophase of the bulk materials was found for the alcohol 2 as indicated by a Maltese Cross texture, whereas the acid 1 remained isotopic. Y1 - 1995 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 - Giebler, Rainer A1 - Schulz, Burkhard A1 - Reiche, Jürgen A1 - Brehmer, Ludwig A1 - Wühn, Mario A1 - Wöll, Christoph A1 - Smith, Andrew Phillip A1 - Urquhart, Steven G. A1 - Ade, Harald W. A1 - Unger, Wolfgang E. S. T1 - Near-edge x-ray absorption fine structure spectroscopy on ordered films of an amphiphilic derivate of 2,5- Diphenyl-1,3,4-oxadiazole N2 - The surfaces of ordered films formed from an amphiphilic derivative of 2,5-diphenyl-1,3,4-oxadiazole by the Langmuir-Blodgett (LB) technique and organic molecular beam deposition (OMBD) were investigated by the use of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. For the assignment of the spectral features of the C, N, and O K- edge absorption spectra, fingerprint spectra of poly(p-phenylene terephthalamide)(Kevlar), poly(ethylene terephthalate), poly(p-phenylene-1,3,4-oxadiazole), and 2,5-di- (pentadecyl)-1,3,4-oxadiazole, which contain related chemical moieties, were recorded. Ab initio molecular orbital calculations, performed with explicit treatment of the core hole, are used to support the spectral interpretations. Angle-resolved NEXAFS spectroscopy at the C, N, and O K-edges suggests a preferentially upright orientation of the oxadiazole derivative in the outermost layer of the films. X-ray specular reflectivity data and molecular modeling results suggest a similar interpretation. Y1 - 1999 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 -