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 - Schulz, Burkhard A1 - Stiller, Burkhard A1 - Zetzsche, Thomas A1 - Knochenhauer, Gerald A1 - Brehmer, Ludwig T1 - Characterization of crystals based on 1,3,4-oxadiazoles by atomic force microscopy N2 - The surface structures of crystals based on aromatic oxadiazoles were investigated by AFM. The crystal structure for 2,5-di(p-tolyl)-1,3,4-oxadiazole (DTO) differs from that of 2,5-di (4-methoxycarbonyl-phenyl)-1,3,4- oxadiazole (DMPO). In DMPO all molecules show parallel orientation to the surface in such a way that the surface is formed as well as by the nitrogen atoms of the heterocyclic rings and the methyl groups of the ester substituents. By contrast, the oxadiazole molecules in DTO crystals are oriented perpendicular to the crystal surface. The experimental data are interpreted by molecular modelling. It is shown that there is a difference between molecular structure of the surface, as detected by AFM, and the bulk structure determined by X-ray diffraction. Y1 - 1997 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 - Schulz, Burkhard A1 - Bruma, Maria A1 - Brehmer, Ludwig T1 - Aromatic poly(1,3,4-oxadiazole)s as advanced materials N2 - Poly(1,3,4-oxadiazole)s have been the focus of considerable interest with regard to the- production of high- performance materials, particularly owing to their high thermal stability in oxidative atmosphere and specific properties determined by the structure of 1,3,4-oxadiazole ring, which, from the spectral and electronic points of view, is similar to a p-phenylene structure.[1] Besides their excellent resistance to high temperature, polyoxadiazoles have many desirable characteristics, such as good hydrolytic stability, high glass transition temperatures, low dielectric constants, and tough mechanical properties. Some polyoxadiazoles have semiconductive properties, other structures can be electrochemically doped and thus made conductive, and other have liquid-crystalline properties, which make them very attractive for a wide range of high-performance applications. They exhibit excellent fiber- and film-forming capabilities, thus being considered for use as heat-resistant reinforcing fibers for advanced composite materials, highly resistant fabrics for the filtration of hot gases, special membranes for gas separation or reverse osmosis, precursors for highly oriented graphite fibers, films, and blocks to be used in the construction of electronic instruments based on X-rays, neutron beams, or a-particles, or in the construction of nuclear reactor walls. Since they were first reported in 1961,[2] a wide variety of polymers containing 1,3,4-oxadiazole rings have been synthesized, and their preparation, characterization, and physico-mechanical properties have been periodically reviewed .[3-8] This article will present a general overview of this class of polymers and will refer to the work carried out by different researchers in the last ten years with the emphasis on the potential uses of such polymers as advanced materials. Y1 - 1997 ER - TY - JOUR A1 - Schulz, Burkhard A1 - Kaminorz, Yvette A1 - Brehmer, Ludwig T1 - New aromatic poly(1,3,4-oxadiazole)s for light emitting diodes N2 - New aromatic poly(1,3,4-oxadiazole)s were synthesized having excellent film forming properties due to their solubility in common organic solvents. The investigated new polyoxadiazoles can be used as emission material in single layer LED. The poly- oxadiazoles show an emission in the range of blue to yellow light. The external quantum efficiency as well as the turn-on voltage of the devices are influenced when blends of the polyoxadiazole with hole transport materials are used. Y1 - 1997 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 - 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 - 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 - 1994 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 - 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 - Schulz, Burkhard A1 - Brehmer, Ludwig A1 - Knochenhauer, Gerald T1 - Supramolecular structures of aromatic 1,3,4-oxadiazole solids Y1 - 1995 ER - TY - JOUR A1 - Kaminorz, Yvette A1 - Schulz, Burkhard A1 - Brehmer, Ludwig T1 - Optical and Electrical Properties of Substituted 2,5-Diphenyl-1,3,4-Oxadiazoles N2 - New substituted 2,5-diphenyl-1,3,4-oxadiazoles are reported as luminescent materials in light emitting diodes LEDs . The investigated new oxadiazoles show efficient blue and green emission in single layer devices. The combination with a hole transporting and red emitting polythiophene led to a white emission with higher quantum efficiency (QE). Y1 - 2000 ER - TY - JOUR A1 - Karageorgiev, Peter A1 - Stiller, Burkhard A1 - Prescher, Dietrich A1 - Dietzel, Birgit A1 - Schulz, Burkhard A1 - Brehmer, Ludwig T1 - Modification of the surface potential of azobenzene-containing langmuir-blodgett films in the near field of a scanning kelvin microscope tip by irradiation Y1 - 2000 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 - 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 - 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 - Karageorgiev, Peter A1 - Neher, Dieter A1 - Schulz, Burkhard A1 - Stiller, Burkhard A1 - Pietsch, Ullrich A1 - Giersig, Michael A1 - Brehmer, Ludwig T1 - From anisotropic photo-fluidity towards nanomanipulation in the optical near-field N2 - An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in which the degree of mechanical anisotropy can be controlled by light. Whereas during irradiation by circular polarized light the film behaves as an isotropic viscoelastic fluid, it shows considerable fluidity only in the direction parallel to the light field vector under linear polarized light. The fluidization phenomenon is related to photoinduced motion of azobenzene-functionalized molecular units, which can be effectively activated only when their transition dipole moments are oriented close to the direction of the light polarization. We also describe here how the photofluidization allows nanoscopic elements of matter to be precisely manipulated Y1 - 2005 SN - 1476-1122 ER -