@article{ZhuSchulzBrumaetal.1996, author = {Zhu, Shigen and Schulz, Burkhard and Bruma, Maria and Brehmer, Ludwig}, title = {Comparative study of the thermal properties of related aromatic polyhydrazides and poly(1,3,4-oxadiazole)s}, issn = {1042-7147}, doi = {10.1002/(SICI)1099-1581(199612)7:12<879::AID-PAT600>3.0.CO;2-X}, year = {1996}, language = {en} } @article{SchulzStillerZetzscheetal.1997, author = {Schulz, Burkhard and Stiller, Burkhard and Zetzsche, Thomas and Knochenhauer, Gerald and Brehmer, Ludwig}, title = {Characterization of crystals based on 1,3,4-oxadiazoles by atomic force microscopy}, year = {1997}, abstract = {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.}, language = {en} } @article{ReicheZetzscheHelmsetal.1997, author = {Reiche, J{\"u}rgen and Zetzsche, Thomas and Helms, Andreas and Freydank, Anke-Christine and Knochenhauer, Gerald and Schulz, Burkhard and Brehmer, Ludwig}, title = {Organized molecular films of oxadiazole compounds formed by vacuum deposition}, year = {1997}, language = {en} } @article{SchulzBrumaBrehmer1997, author = {Schulz, Burkhard and Bruma, Maria and Brehmer, Ludwig}, title = {Aromatic poly(1,3,4-oxadiazole)s as advanced materials}, year = {1997}, abstract = {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.}, language = {en} } @article{SchulzKaminorzBrehmer1997, author = {Schulz, Burkhard and Kaminorz, Yvette and Brehmer, Ludwig}, title = {New aromatic poly(1,3,4-oxadiazole)s for light emitting diodes}, year = {1997}, abstract = {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.}, language = {en} } @article{SchulzBrehmerDietzeletal.1995, author = {Schulz, Burkhard and Brehmer, Ludwig and Dietzel, Birgit and Zetzsche, Thomas}, title = {Preparation and characterization of ordered thin films based on aromatic poly(1,3,4-oxadiazole)s}, year = {1995}, language = {en} } @article{SchulzKnochenhauerBrehmeretal.1995, author = {Schulz, Burkhard and Knochenhauer, Gerald and Brehmer, Ludwig and Janietz, Silvia}, title = {Stuctures and properties of aromatic poly(1,3,4-oxadiazole)s}, year = {1995}, language = {en} } @article{SchulzStillerZetzscheetal.1995, author = {Schulz, Burkhard and Stiller, Burkhard and Zetzsche, Thomas and Knochenhauer, Gerald and Dietel, Reinhard and Brehmer, Ludwig}, title = {Characterization of 2,5-di(p-tolyl-1,3,4- oxadiazole) crystals by IR-spectroscopy and atomic force microscopy}, year = {1995}, language = {en} } @article{SchulzStillerZetzscheetal.1994, author = {Schulz, Burkhard and Stiller, Burkhard and Zetzsche, Thomas and Knochenhauer, Gerald and Dietel, Reinhard and Brehmer, Ludwig}, title = {Crystal structure of 2,5-Di(4- methoxycarbonyl-phenyl)-1,3,4-oxadiazole characterized by AFM and IR- spectroscopy}, year = {1994}, language = {en} } @article{SchulzKnochenhauerBrehmeretal.1994, author = {Schulz, Burkhard and Knochenhauer, Gerald and Brehmer, Ludwig and Janietz, Silvia}, title = {Stuctures and properties of aromatic poly(1,3,4-oxadiazole)s}, year = {1994}, language = {en} } @article{ReicheSchulzKnochenhaueretal.1997, author = {Reiche, J{\"u}rgen and Schulz, Burkhard and Knochenhauer, Gerald and Dietzel, Birgit and Freydank, Anke-Christine and Zetzsche, Thomas and Brehmer, Ludwig}, title = {Supramolecular structures formed from heterocyclic aromatic molecules}, year = {1997}, abstract = {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.}, language = {en} } @article{SchulzBrehmer1995, author = {Schulz, Burkhard and Brehmer, Ludwig}, title = {Preparation and characterization of ordered thin films based on aromatic poly(1,3,4-oxadiazole)s}, year = {1995}, language = {en} } @article{SchulzBrehmerKnochenhauer1995, author = {Schulz, Burkhard and Brehmer, Ludwig and Knochenhauer, Gerald}, title = {Supramolecular structures of aromatic 1,3,4-oxadiazole solids}, year = {1995}, language = {en} } @article{KaminorzSchulzBrehmer2000, author = {Kaminorz, Yvette and Schulz, Burkhard and Brehmer, Ludwig}, title = {Optical and Electrical Properties of Substituted 2,5-Diphenyl-1,3,4-Oxadiazoles}, year = {2000}, abstract = {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).}, language = {en} } @article{KarageorgievStillerPrescheretal.2000, author = {Karageorgiev, Peter and Stiller, Burkhard and Prescher, Dietrich and Dietzel, Birgit and Schulz, Burkhard and Brehmer, Ludwig}, title = {Modification of the surface potential of azobenzene-containing langmuir-blodgett films in the near field of a scanning kelvin microscope tip by irradiation}, year = {2000}, language = {en} } @article{GieblerSchulzReicheetal.1999, author = {Giebler, Rainer and Schulz, Burkhard and Reiche, J{\"u}rgen and Brehmer, Ludwig and W{\"u}hn, Mario and W{\"o}ll, Christoph and Smith, Andrew Phillip and Urquhart, Steven G. and Ade, Harald W. and Unger, Wolfgang E. S.}, title = {Near-edge x-ray absorption fine structure spectroscopy on ordered films of an amphiphilic derivate of 2,5- Diphenyl-1,3,4-oxadiazole}, year = {1999}, abstract = {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.}, language = {en} } @article{ReicheFreydankHelmsetal.1999, author = {Reiche, J{\"u}rgen and Freydank, Anke-Christine and Helms, Andreas and Geue, Thomas and Schulz, Burkhard and Brehmer, Ludwig and Stiller, Burkhard and Knochenhauer, Gerald}, title = {Vacuum deposition films of oxadiazole compounds : formation and structure investigation}, year = {1999}, abstract = {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.}, language = {en} } @article{SchuermannKochImperiaetal.1999, author = {Sch{\"u}rmann, H. and Koch, Norbert and Imperia, Paolo and Schrader, Sigurd and Jandke, M. and Strohriegl, P. and Schulz, Burkhard and Leising, G. and Brehmer, Ludwig}, title = {Ultraviolet photoelectron spectroscopic study of heterocyclic model compounds for electroluminescent devices}, year = {1999}, language = {en} } @article{KarageorgievNeherSchulzetal.2005, author = {Karageorgiev, Peter and Neher, Dieter and Schulz, Burkhard and Stiller, Burkhard and Pietsch, Ullrich and Giersig, Michael and Brehmer, Ludwig}, title = {From anisotropic photo-fluidity towards nanomanipulation in the optical near-field}, issn = {1476-1122}, year = {2005}, abstract = {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}, language = {en} }