Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen OPUS4-24407 Wissenschaftlicher Artikel Bruma, Maria; Hamciuc, Corneliu; Hamciuc, Elena; Mercer, Frank W.; Belomoina, Nataliya; Schulz, Burkhard Heterocyclic polyamides containing hexafluoroisopropylidene groups New heterocyclic polyamides have been synthesized by solution polycondensation of aromatic diamines containing phenyl- quinoxaline units with diacid chlorides having both imide and hexafluoroisopropylidene (6F) groups. These polymers are soluble in polar aprotic solvents, such as N-methylpyrrolidone (NMP) or N,N-dimethylformamide (DMF), and can be cast into flexible thin films from solutions. They show high thermooxidative stability with decomposition temperatures above 400°C and glass transition temperatures in the range of 225 - 300°C. The polymer films exhibit good chemical resistance towards deluted acids and good electrical insulating properties with dielectric constants in the range of 3.2 - 3.7. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24403 Wissenschaftlicher Artikel Lavrenko, Peter N.; Schulz, Burkhard; Strelina, Irina A.; Okatova, Olga V. Synthesis and molecular properties of new poly(naphthalene-1,3,4-oxadiazole)s Poly[(1,4-naphthalene)-2,5-diyl-1,3,4-oxadiazole] and poly[(2,6-naphthalene)-2,5-diyl-1,3,4-oxadiazole] have been synthesized and investigated in conc. H2S04, by the flow birefringence method in comparison with poly(1,4- phenylene)-2,5-diyl-1,3,4-oxadiazole]. Changes in conformation parameters and optical anisotropy of a chain unit induced by incorporation of the naphthalene groups into the macromolecule backbone have been evaluated. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24401 Wissenschaftlicher Artikel Sava, Ion; Szesztay, Marta; Bruma, Maria; Mercer, Frank W.; Schulz, Burkhard Compared properties of aromatic polyamides containing silicon in the chain Two series of aromatic polyamides incorporating silicon together with phenylquinoxaline or with hexafluoroisopropylidene groups have been synthesized and their properties have been characterized and compared with those of related polymers. These polymers are easily soluble in polar amidic solvents such as N-rnethyl-2-pyrrolidinone and dimethylformamide, and in tetrahydrofuran, and can be cast into thin, transparent films from solution. The polyamides have weight- and number-average molecular weights in the range of 10000-40000 and 3000-6000, respectively, and polydispersities in the range of 3-10. They show glass transition temperatures in the range of 236 °C-275 °C and decomposition temperatures above 400 °C. The polymer films have low dielectric constants in the range of 3.26-3.68, and good mechanical properties (tensile strength 74-100 MPa, tensile modulus 180-386 MPa), thus being comparable with other high performance dielectrics. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24400 Wissenschaftlicher Artikel Schulz, Burkhard; Bruma, Maria; Brehmer, Ludwig Aromatic poly(1,3,4-oxadiazole)s as advanced materials 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. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24397 Wissenschaftlicher Artikel Sava, Ion; Bruma, Maria; Schulz, Burkhard; Mercer, Frank W.; Belomoina, Nataliya Synthesis and Properties of Silicon-containing Polyamides A series of aromatic polyamides incorporating silicon together with phenylquinoxaline or with hexafluoroisopropylidene groups has been synthesized by solution polycondensation of a silicon-containing diacid chloride with aromatic diamines having phenylquinoxaline rings or hexafluoroisopropylidene groups. These polymers are easily soluble in polar aprotic solvents, such as N-methylpyrrolidinone and dimethylformamide, and in tetrahydrofurane, and can be solution-cast into thin, transparent films having low dielectric constant, in the range of 3.26 to 3.68. These polymers show high thermal stability with decomposition temperature being above 400 °C and glass transition temperature in the range of 236 °C to 275 °C. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24396 Wissenschaftlicher Artikel Schulz, Burkhard; Kaminorz, Yvette; Brehmer, Ludwig New aromatic poly(1,3,4-oxadiazole)s for light emitting diodes 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. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24395 Wissenschaftlicher Artikel Lavrenko, Peter N.; Strelina, Irina A.; Schulz, Burkhard Dynamo-optical properties of poly(naphthylene oxadiazole)s in sulfuric acid Flow birefringence induced in dilute solutions of poly[(1,4-naphthylene)-2,5-diyl-1,3,4-oxadiazole] and poly[2,6-naphthylene)-2,5-diyl-1,3,4-oxadiazole] in conc. sulphuric acid has been investigated. The shear optical coefficient was found for these polymers to be approximately double the value of that obtained in the same solvent for poly[(para-phenylene) -2,5-diyl-1,3,4-oxadiazole]. Rigid-chain behaviour of the polymers was characterized by hydrodynamic and dynamo-optical parameters evaluated with application of the worm-like chain model and the "method of similar structures". Change in optical anisotropy of a chain unit induced by incorporation of naphthylene groups into the main chain has been evaluated. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24335 Wissenschaftlicher Artikel Schulz, Burkhard; Stiller, Burkhard; Zetzsche, Thomas; Knochenhauer, Gerald; Brehmer, Ludwig Characterization of crystals based on 1,3,4-oxadiazoles by atomic force microscopy 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. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24334 Wissenschaftlicher Artikel Orgzall, Ingo; Lorenz, Bernd; Mikat, Jürgen E. R.; Dietel, Reinhard; Knochenhauer, Gerald; Schulz, Burkhard Raman and IR spectroscopic investigation of aromatic 1,3,4-oxadiazole polymers and oligomers The molecular structure of poly(p-phenylene-1,3,4-oxadiazole) (POD) is investigated using i.r. and Raman spectroscopy. Both methods reveal characteristic differences for the a- and b-POD forms that are most obvious in the spectral region between 1500 and 1650 cm-1. The spectra for dimer and tetramer compounds already show the same features as found for longer chains. Based on molecular modelling calculations these differences are assigned to cis and trans conformations of the main chain segments. High pressure measurements show a linear shift of the Raman lines and support the result of the thermodynamic stability of the trans conformation. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten OPUS4-24333 Wissenschaftlicher Artikel Hamciuc, Elena; Hamciuc, Corneliu; Bruma, Maria; Stoleriu, Andre; Schulz, Burkhard Poly(hydrazide-ester)s and poly(1,3,4-oxadiazole-ester)s containing pendent phenoxy groups A series of new arornatic poly(hydrazide-ester)s has been synthesized by solution polycondensation of two diacid dichlorides containing preformed ester groups with phenoxyterephthaloyl dihydrazide or with a mixture of phenoxyterephthaloyl dihydrazide with terephthaloyl- or isophthaloyl dihydrazide in N-methyl-2-pyrrolidinone. The thermal cyclization of the poly(hydrazide-ester)s gave the corresponding poly(1,3,4-oxadiazole-ester)s containing pendent phenoxy groups. The polymers were characterized by viscometry, solubility measurements, IR spectroscopy, differential scanning calorimetry and thermogravimetric analysis. 1997 Interdisziplinäres Zentrum für Dünne Organische und Biochemische Schichten