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Eingeladener Vortrag
- nein (2)
Intrinsically conductive plasma polymers were formed in a 2.45 GHz microwave low pressure plasma. The electrical conductivity and structure of the polymeric films were compared with those of electrochemically polymerized polythiophene. A new method of doping was tested using the iodine-containing monomer 2-iodothiopene. Films with high electrical conductivity (10-1 down to 10-6 S cm-1) could be produced, and their chemical structure was studied by X-ray photoelectron spectroscopy and Fourier transform IR spectroscopy. The IR spectra give a strong indication that the chemical structure of these films is comparable with that of electrochemically deposited polythiophene. Optical emission spectroscopy was used to give in-situ information about the fragmentation mechanism in the plasma.
Conjugated polymers based on 1,4-phenylenevinylene units are very promising materials for applications as light-emitting diodes. A major requirement is their stability at elevated temperatures of operation. The thermo-oxidative behaviour of a soluble poly(1,4-phenylenevinylene) derivative, poly[2,5-bis(2-ethylhexyloxy)-1,4-phenylene vinylene], was investigated by using chemiluminescence and UVVis absorption spectroscopy. Extremely sensitive chemiluminescence is successfully applied since even minor chemical changes could lead to a considerable loss of photo- and electro-optical properties. Various degradation processes are described as a function of time and temperature and their influences on functional properties are discussed. The investigated material does not show sufficient thermo-oxidative stability within the temperature range of intended use in contact with air. For industrial application, direct contact with oxygen during processing and operation has to be avoided.
Structural investigations of electrical conducting plasma polymerized films from 2-iodothiophene
(1993)
Thin plasma polymerized films were produced in a microwave (2.45 GHz) plasma discharge using 2-iodothiophene as the initial monomer. The structure of these electrically conducting films (10-6-10-1 S/cm), the chemical state of the doping element iodine and the elemental homogeneity at the surface and in the films have been investigated by XPS, FTIR and AES. An interesting relationship was found that indicates some similarity to conventional polythiophene, prepared by electrodeposition. Besides covalently bound iodine, considerable amounts of I 3- and I 5- were detected and also a small number of O-I bonds were identified.
Polarized fluorescence and orientational order parameters of a liquid-crystalline conjugated polymer
(1999)
We report a study of the orientational order of aligned thin films of the liquid crystalline conjugated polymer poly(9,9-dioctylfluorene). Steady state polarized fluorescence measurements were used to determine the orientational order parameter <P2> and <P4>. The influence of intermolecular and intramolecular excitation energy transfer on the degree of polarization is discussed. The role of film morphology is also examined by comparison of the results for glassy and crystalline films.
Polarized fluorescence and orientational order parameters of a liquid crystalline conjugated polymer
(1999)
In films of poly(para-phenylphenylenevinylene) a photoreaction has been observed. The significant feature is a decrease of the fluorescence emission intensity during irradiation. It is assumed that a cycloaddition between C=C- double-bonds leads to crosslinks in the material.
Under similar conditions of excitation a photoreaction has not been observed in poly(p-phenylenevinylene) prepared via the precursor-route.