TY - JOUR A1 - Meier, Johann Georg A1 - Stumpe, Joachim A1 - Fischer, Birgit A1 - Thieme, Cathrin A1 - Fischer, Thomas M. A1 - Kremer, Friedrich A1 - Öge, Tanja A1 - Zentel, Rudolf T1 - Optical suppression of Ferroelectricity in polysiloxane copolymers with chiral an potochromic side groups Y1 - 1998 ER - TY - JOUR A1 - Anton, Arthur Markus A1 - Steyrleuthner, Robert A1 - Kossack, Wilhelm A1 - Neher, Dieter A1 - Kremer, Friedrich T1 - Infrared Transition Moment Orientational Analysis on the Structural Organization of the Distinct Molecular Subunits in Thin Layers of a High Mobility n-Type Copolymer JF - Journal of the American Chemical Society N2 - The IR-based method of infrared transition moment orientational analysis (IR-TMOA) is employed to unravel molecular order in thin layers of the semiconducting polymer poly[N,N'-bis(2-octyldodecyl),-1,4,5,8-naphthalene-diimide-2,6-diyl]-alt-5-5'-(2,2'-bithiophene) (P(NDI2OD-T2)). Structure-specific vibrational bands are analyzed in dependence On polarization and inclination of the sample-With respect to the optical axis. By that the molecular Order parameter tensor for the respective molecular moieties with regard to the sample: coordinate system is deduced. Making use of the specificity of the IR spectral range, we are able to determine separately the orientation of atomistic planes defined through the naphthalenediimide (NDI) and bithiophene (T2) units relative to the substrate, and hence, relative to each other. A pronounced solvent effect is observed While chlorobenzene causes the T2 planes to align preferentially parallel to the substrate at an angle of 29 degrees, using a 1:1 chloronaphthalene:xylene mixture results in a reorientation of the T2 units from a face on into an edge on arrangement. In contrast the NDI unit remains unaffected. Additionally, for both solvents evidence is observed for the aggregation of chains in accord With recently published results obtained by UV-vis absorption spectroscopy. Y1 - 2015 U6 - https://doi.org/10.1021/jacs.5b01755 SN - 0002-7863 VL - 137 IS - 18 SP - 6034 EP - 6043 PB - American Chemical Society CY - Washington ER - TY - GEN A1 - Rozanski, Stanislaw A. A1 - Kremer, Friedrich A1 - Köberle, Peter A1 - Laschewsky, André T1 - Relaxation and charge transport in mixtures of zwitterionic polymers and inorganic salts N2 - Dielectric spectroscopy is employed to analyze the molecular dynamics and the charge transport in mixtures of zwitterionic polymers of the type poly{3 [N(-methacryloyloxyalkyl)] N, [N-dimethylammonio propanesulfonate] with sodium iodide in the frequency range of 10²Hz-10(up)7 Hz and in the temperature range of 110 K-400 K. The amount of inorganic salt added varies from 0-200 mol-% relative to the number of zwitterionic groups present in the polymer, contributing strongly to the conductivity. One relaxation process is observed whose relaxation rate depends strongly on the length of the aliphatic spacer between the polymethacrylate main chain and the zwitterionic group. Exhibiting an Arrhenius-like temperature depence with activation energy EA = 47 KJ/mol, this relaxation process is assigned to fluctuation of the quaternary ammonium groups in the side chains. At higher temperatures, the dielectric properties and the conductivity are primarily dominated by the mobile inorganic ions: conductivity strongly depends on the salt concentration, showing a pronounced electrode polarization effect. The frequency and salt concentration, dependences of the conductivity can be quantitatively described as hopping of charge carriers being subject to spatially randomly varying energy barriers. For the low-frequency regime and for the critical frequency marking the onset of the conductivity's dispersion, the Barton-Nakajima-Namikawa (BNN) relationship is fulfilled. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 093 Y1 - 1995 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17438 ER - TY - JOUR A1 - Kathrein, Christine C. A1 - Kipnusu, Wycliffe K. A1 - Kremer, Friedrich A1 - Böker, Alexander T1 - Birefringence Analysis of the Effect of Electric Fields on the Order-Disorder Transition Temperature of Lamellae Forming Block Copolymers JF - Macromolecules : a publication of the American Chemical Society N2 - A detailed birefringence analysis of the effect of strong dc electric fields on the order-disorder transition temperature (T-ODT) of lamella forming block copolymers is reported. The setup presented here enabled the measurement of the T-ODT with high temperature resolution while the birefringence measurements were nondestructive and straightforward compared to alternative methods. A downward shift in the transition temperature was found for all samples upon application of the electric field. The data indicate that the dominating parameter that evokes the mixing of block copolymers when exposed to electric fields is the difference in dielectric permittivity Delta epsilon between the block copolymer constituents. The extent to which the T-ODT is shifted is furthermore influenced by the degree of polymerization N. Shifts in the transition temperature of up to 7 degrees C were found upon application of an electric field of 5 kV/mm. Y1 - 2015 U6 - https://doi.org/10.1021/acs.macromol.5b00512 SN - 0024-9297 SN - 1520-5835 VL - 48 IS - 10 SP - 3354 EP - 3359 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Holländer, Lars A1 - Kossack, Wilhelm A1 - Kollosche, Matthias A1 - Wirges, Werner A1 - Kremer, Friedrich A1 - Gerhard, Reimund T1 - Influence of the remanent polarisation on the liquid crystal alignment in composite films of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and a cyanobiphenyl-based liquid crystal JF - Liquid crystals : an international journal of science and technology N2 - Polymer-dispersed liquid crystals (PDLCs) of ferroelectric poly(vinylidene fluoride-trifluoroethylene) and nematic 4-cyano-4ʹ-n-hexylbiphenyl (6CB) or 4-cyano-4ʹ-n-pentylbiphenyl (5CB) were prepared to study the effect of the remanent polarisation of the polymer on the liquid crystal alignment. We measured the macroscopic alignment of the liquid crystal molecules in the thickness direction by means of Infrared Transition-Moment Orientational Analysis. Electrical poling at 100 V/µm caused an increased order parameter up to 0.15. After subsequent annealing above the nematic-to-isotropic phase-transition temperature, the order parameter was reduced to 0.02. Nevertheless, the order parameter was still higher than for non-poled film indicating a slight orientation in thickness direction. Both values are lower than those expected from model calculations. In agreement with dielectric measurements, we attribute this result to the shielding effect of mobile charge carriers within the liquid crystal inclusions. KW - Polymer-dispersed liquid crystal KW - ferroelectric polymer KW - remanent polarisation KW - liquid crystal alignment Y1 - 2016 U6 - https://doi.org/10.1080/02678292.2016.1185174 SN - 0267-8292 SN - 1366-5855 VL - 43 SP - 1514 EP - 1521 PB - Editions Rodopi BV CY - Abingdon ER -