TY - JOUR A1 - Yusupov, R. G. A1 - Frübing, Peter A1 - Brehmer, Ludwig A1 - Mislavski, B. V. T1 - Langmuir Filme des Polymers "NAFION" als sensibles Element eines Feuchtesensors Y1 - 1995 ER - TY - JOUR A1 - Wang, Feipeng A1 - Lack, Alexander A1 - Xie, Zailai A1 - Frübing, Peter A1 - Taubert, Andreas A1 - Gerhard, Reimund T1 - Ionic-liquid-induced ferroelectric polarization in poly(vinylidene fluoride) thin films JF - Applied physics letters N2 - Thin films of ferroelectric beta-phase poly(vinylidene fluoride) (PVDF) were spin-coated from a solution that contained small amounts of the ionic liquid (IL) 1-ethyl-3-methylimidazolium nitrate. A remanent polarization of 60 mC/m(2) and a quasi-static pyroelectric coefficient of 19 mu C/m(2)K at 30 degrees C were observed in the films. It is suggested that the IL promotes the formation of the beta phase through dipolar interactions between PVDF chain-molecules and the IL. The dipolar interactions are identified as Coulomb attraction between hydrogen atoms in PVDF chains and anions in IL. The strong crystallinity increase is probably caused by the same dipolar interaction as well. KW - dielectric polarisation KW - ferroelectric thin films KW - polymer films KW - pyroelectricity KW - spin coating Y1 - 2012 U6 - https://doi.org/10.1063/1.3683526 SN - 0003-6951 VL - 100 IS - 6 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Wang, Feipeng A1 - Frübing, Peter A1 - Wirges, Werner A1 - Gerhard, Reimund A1 - Wegener, Michael T1 - Enhanced Polarization in Melt-quenched and Stretched Poly(vinylidene Fluoride-Hexafluoropropylene) Films N2 - beta-phase poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymer films were prepared by uniaxially stretching solution-cast or melt-quenched samples. Different preparation routes lead to different amounts of the crystalline alpha and beta phases in the films, as detected by means of Fourier-transform infrared spectroscopy and X-ray diffractometry. The beta phase is significantly enhanced in melt-quenched and stretched films in comparison to solution-cast and stretched films. This is particularly true for copolymer samples with higher HFP content. The beta- phase enhancement is also observed in ferroelectric-hysteresis experiments where a rather high polarization of 58 mC/ m(2) was found on melt-quenched and stretched samples after poling at electric fields of 140 MV/m. After poling at 160 MV/m, one of these samples exhibited a piezoelectric d(33) coefficient as high as 21 pC/N. An electric-field-induced partial transition from the alpha to the beta phase was also observed on the melt-quenched and stretched samples. This effect leads to a further increase in the applications-relevant dipole polarization. Uniaxially stretched ferroelectric- polymer films are highly anisotropic. Dielectric resonance spectroscopy reveals a strong increase of the transverse piezoelectric d(32) coefficient and a strong decrease of the transverse elastic modulus c(32) upon heating from 20 to 50 degrees C. Y1 - 2010 UR - http://ieeexplore.ieee.org/servlet/opac?punumber=94 U6 - https://doi.org/10.1109/TDEI.2010.5539679 SN - 1070-9878 ER - TY - JOUR A1 - Raman Venkatesan, Thulasinath A1 - Gulyakova, Anna A. A1 - Frübing, Peter A1 - Gerhard, Reimund T1 - Electrical polarization phenomena, dielectric relaxations and structural transitions in a relaxor-ferroelectric terpolymer investigated with electrical probing techniques JF - Materials research express N2 - Dielectric Relaxation Spectroscopy (DRS) and Thermally Stimulated Depolarization Current (TSDC) measurements were employed to study dielectric-relaxation processes, structural transitions and electric-polarization phenomena in poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films. Results from DRS confirm the existence of two separate dispersion regions related to a para-to-ferroelectric phase transition and to the glass transition. The dipolar TSDC peak correlates with the loss peak of the ? relaxation that represents the glass transition. The electric polarization calculated from the dipolar TSDC peak (glass transition) shows a non-linear electric-field dependence and saturates at high electric poling fields. As the observed behaviour is essentially the same as that of the electric polarization obtained from direct polarization-versus-electric-field hysteresis measurements, TSDC experiments are also suitable for studying the polarization in relaxor-ferroelectric polymers. A saturation polarization of 44 mC m(?2) was found for an electric field of 190 MV m(?1). KW - P(VDF-TrFE-CFE) terpolymer KW - relaxor-ferroelectric polymers KW - dielectric relaxation spectroscopy KW - thermally stimulated depolarization current KW - electrical polarization hysteresis Y1 - 2019 U6 - https://doi.org/10.1088/2053-1591/ab5352 SN - 2053-1591 VL - 6 IS - 12 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Raman Venkatesan, Thulasinath A1 - Gulyakova, Anna A. A1 - Frübing, Peter A1 - Gerhard, Reimund T1 - Relaxation processes and structural transitions in poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) relaxor-ferroelectric terpolymers as seen in dielectric spectroscopy JF - IEEE transactions on dielectrics and electrical insulation N2 - Dielectric relaxation processes and structural transitions in Poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films with two different monomer compositions were investigated in comparison with Poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer films as reference material. Differential Scanning Calorimetry was employed to assess annealing effects on phase transitions and crystalline structure, while relaxation processes were investigated by means of Dielectric Relaxation Spectroscopy, the results of which indicate the existence of two separate dispersion regions, denoted as processes A and B, respectively. Process A appears at a certain temperature independent of frequency, but is strongly influenced by the crystallisation temperature and the CFE content, while peak B shows typical features of a relaxation process and is less influenced by crystallisation temperature and CFE content. Furthermore, peak B is related to the glass transition which is more pronounced in the terpolymer than in P(VDF-TrFE). A closer analysis indicates that the addition of CFE and thermal annealing gradually shift the ferro-to-paraelectric transition in P(VDF-TrFE) to lower temperatures, while the phase transition is transformed more and more into a relaxation. KW - P(VDF-TrFE-CFE) terpolymer KW - relaxor-ferroelectric polymer KW - dielectric relaxation spectroscopy KW - Curie transition KW - differential scanning calorimetry Y1 - 2018 U6 - https://doi.org/10.1109/TDEI.2018.007440 SN - 1070-9878 SN - 1558-4135 VL - 25 IS - 6 SP - 2229 EP - 2235 PB - Institut of Electrical and Electronics Engineers CY - Piscataway ER - TY - GEN A1 - Raman Venkatesan, Thulasinath A1 - Frübing, Peter A1 - Gerhard, Reimund T1 - Influence of Composition and Preparation on Crystalline Phases and Morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) Relaxor-Ferroelectric Terpolymer T2 - 2018 IEEE 2nd International Conference on Dielectrics (ICD) N2 - The influence of chemical composition and crystallisation conditions on the ferroelectric and paraelectric phases and the resulting morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films with 55.4/37.2/7.3 mol% or with 62.2/29.4/8.4 mol% of VDF/TrFE/CFE was studied. Poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) with 75/25 mol% VDF/TrFE was employed as reference material. Fourier-Transform Infrared Spectroscopy (FTIR) was used to determine the fractions of the relevant terpolymer phases, and X-Ray Diffraction (XRD) was employed to assess the crystalline morphology. The FTIR results show an increase of the fraction of paraelectric phases after annealing. On the other hand, XRD results indicate a more stable paraelectric phase in the terpolymer with higher CFE content. KW - P(VDF-TrFE-CFE) terpolymer KW - relaxor-ferroelectric polymer KW - ferroelectric and paraelectric phases KW - Curie transition Y1 - 2018 SN - 978-1-5386-6389-9 U6 - https://doi.org/10.1109/ICD.2018.8514758 PB - IEEE CY - New York ER - TY - JOUR A1 - Penacorada, Florencio A1 - Yusupov, R. G. A1 - Milaski, B. A1 - Frübing, Peter A1 - Brehmer, Ludwig T1 - Elektrische Eigenschaften von polyionischen LB-Filmen Y1 - 1995 ER - TY - JOUR A1 - Neumann, Bernhard A1 - Horstkemper, Marianne A1 - Krüger, Wolfgang A1 - Wilkens, Martin A1 - Bohlen, Andreas A1 - Frübing, Peter A1 - Wegener, Michael A1 - Scheff, Ullrich A1 - Neher, Dieter A1 - Brehmer, Ludwig A1 - Kleinpeter, Erich A1 - Wolf, Gunter A1 - Koetz, Joachim A1 - Peter, Martin G. A1 - Senkbeil, Sigrid A1 - Meyer, Till T1 - Portal = Im Trend: Physiker und Chemiker erforschen "Soft Matter" BT - Die Potsdamer Universitätszeitung N2 - Aus dem Inhalt: Im Trend: Physiker und Chemiker erforschen „Soft Matter“ -Brandenburger Netzwerk für Existenzgründer erhält Förderung -Universität leistet Beitrag zum Romantik-Jahr -Musiksender MTV und Bryan Adams auf dem Campus T3 - Portal: Das Potsdamer Universitätsmagazin - 06/2002 Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-501441 SN - 1618-6893 VL - 2002 ER - TY - JOUR A1 - Mellinger, Axel A1 - Frübing, Peter A1 - Prescher, Dietrich A1 - Gerhard, Reimund T1 - Dielectric spectra of a partially fluorinated chromophore / amorphous Teflon AF guest-host system Y1 - 1999 ER - TY - JOUR A1 - Künstler, Wolfgang A1 - Frübing, Peter A1 - Gerhard, Reimund A1 - Cerny, J. A1 - Klemberg-Sapieha, J. A1 - Martinu, L. A1 - Wertheimer, M. R. A1 - Holländer, A. A1 - Behnisch, Juergen T1 - Surface-charging behavior of plasma-treated polymer films Y1 - 1998 ER - TY - JOUR A1 - Kollsche, Matthias A1 - Kalbitz, Rene A1 - Kappel, Marcel A1 - Frübing, Peter A1 - Gerhard, Reimund T1 - Vermittlung von Schlüsselkompetenzen für Biologen in der Studieneingangsphase Y1 - 2012 SN - 978-3- 937026-77-0 ER - TY - JOUR A1 - Kalbitz, Rene A1 - Frübing, Peter A1 - Gerhard, Reimund A1 - Taylor, D. M. T1 - Stability of polarization in organic ferroelectric metal-insulator-semiconductor structures JF - Applied physics letters N2 - Dielectric measurements have been carried out on all-organic metal-insulator-semiconductor structures with the ferroelectric polymer poly(vinylidenefluoride-trifluoroethylene) as the gate insulator. It is shown that the polarization states remain stable after poling with accumulation and depletion voltage. However, negative charge trapped at the semiconductor-insulator interface during the depletion cycle masks the negative shift in flatband voltage expected during the sweep to accumulation voltages. Y1 - 2011 U6 - https://doi.org/10.1063/1.3543632 SN - 0003-6951 VL - 98 IS - 3 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Höpfner, Ulf A1 - Frübing, Peter A1 - Neumann, Werner A1 - Kaminorz, Yvette A1 - Brehmer, Ludwig T1 - Polarization Processes of poly(DMDAAC) films studied by TSD current Y1 - 1996 ER - TY - JOUR A1 - Guliakova, A. A. A1 - Gorokhovatsky, Yu. A. A1 - Galikhanov, M. F. A1 - Frübing, Peter T1 - Thermoactivational spectroscopy of the high impact polystyrene based composite films T1 - Термоактивационная спектроскопия композитных полимерных пленок на основе ударопрочного полистирола JF - St. Petersburg Polytechnic University Journal : Physics and Mathematics N2 - The relaxation processes in the high impact polystyrene (HIPS) films filled with 2, 4, 6 vol.% of titanium dioxide (TiO2) of the rutile modification have been studied using the thermally stimulated depolarization current (TSDC) technique. Three relaxation processes were observed in the composite HIPS films. The first one (a-relaxation peak) appeared at about 93 degrees C and represented the glass transition. The second peak p was a high-temperature part of the first one and overlapped it. The p peak was caused by the release and subsequent motion of excess charges deposited during the electret preparation or the polarization process. The third peak appeared at about 150 degrees C and occurred only in the spectra of the composite films. The overlapping peaks were separated by the thermal cleaning technique. The subsequent application of the numerical methods (the Tikhonov regularization technique) allowed to determine the activation energy of the second process and to compare the obtained value with the corresponding data on the dielectric relaxation. N2 - С помощью метода токов термостимулированной деполяризации (ТСД) исследованы релаксационные процессы в пленках ударопрочного полистирола (УПС) без наполнителя и с различным содержанием диоксида титана TiO2 (2, 4, 6 об.%). На кривых тока ТСД, полученных для композитных пленок, обнаружено три пика. Первый (α-релаксация) возникает при температуре около 93 °C и соответствует переходу вещества из стеклообразного состояния в высокоэластическое. Второй (ρ-пик) появляется как высокотемпературное плечо α-пика и соответствует процессу высвобождения и движения избыточных носителей заряда. Наличие третьего пика при температуре около 150 ºС характерно только для композитных пленок УПС. Разделение перекрывающихся α- и ρ-пиков проведено методом частичной термоочистки. Последующее применение регуляризующих алгоритмов Тихонова позволило определить энергию активации второго процесcа и сравнить полученное значение с результатом, полученным методом диэлектрической спектроскопии. KW - thermoactivational spectroscopy KW - high impact polystyrene KW - titanium dioxide Y1 - 2019 U6 - https://doi.org/10.18721/JPM.12401 SN - 2405-7223 SN - 2618-8686 SN - 2304-9782 VL - 12 IS - 4 SP - 9 EP - 16 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ganesan, Lakshmi Meena A1 - Frübing, Peter A1 - Mellinger, Axel A1 - Gerhard, Reimund T1 - Dielectric relaxation behaviour of nematic liquid crystals dispersed in poly(vinylidene fluoride- trifluoroethylene) N2 - Polymer-dispersed liquid crystals (PDLCs) are prepared from poly(vinylidene fluoride-trifluoroethylene) (P(VDF- TrFE)) and a nematic liquid-crystal (LC). The anchoring effect was studied using dielectric relaxation spectroscopy. Two dispersion regions are observed in the dielectric spectra of the pure P(VDF-TrFE) film. They are related to the glass transition and to a space-charge relaxation. In PDLC films containing 10 wt% of LC, an additional, bias field-dependent relaxation peak is found that can be attributed to the motion of LC molecules. Due to the hindered movement of the LC molecules, this relaxation process is considerably slowed down, compared with the related process in the pure LC. Y1 - 2009 UR - http://iopscience.iop.org/0022-3727/ U6 - https://doi.org/10.1088/0022-3727/42/9/092006 SN - 0022-3727 ER - TY - JOUR A1 - Frübing, Peter A1 - Wegener, Michael A1 - Gerhard, Reimund A1 - Buchsteiner, Alexandra A1 - Neumann, Werner A1 - Brehmer, Ludwig A1 - Dietel, Reinhard T1 - Pyroelectric properties and dielectric hysteresis of a poly(vinylalcohol) with azobenzene alkoxy side chains Y1 - 1999 ER - TY - JOUR A1 - Frübing, Peter A1 - Wegener, Michael A1 - Gerhard, Reimund A1 - Buchsteiner, Alexandra A1 - Neumann, Werner A1 - Brehmer, Ludwig T1 - Different molecular mechanisms for the dielectric hysteresis and pyroelectricity in a poly(vinyl alcohol) with azobenzene-alkoxy side chains N2 - By means of pyroelectrical measurements and dielectric spectroscopy as well as structural information from differential scanning calorimetry, it is shown that, in a poly(vinyl alcohol) with azobenzene-alkoxy side chains, pyroelctricity and dielectric hysteresis which are usually related to each other have different origins. The pyroelectric effect is explained with reversible dipole-density changes upon thermal expansion, whereas the dielectric hysteresis is proposed to result from a charge-carrier polarisation. Y1 - 1999 SN - 0277-786X ER - TY - JOUR A1 - Frübing, Peter A1 - Wang, Feipeng A1 - Wagener, Michael T1 - Relaxation processes and structural transitions in stretched films of polyvinylidene fluoride and its copolymer with hexafluoropropylene JF - Applied physics : A, Materials science & processing N2 - Relaxation processes and structural transitions in nonstretched and uniaxially stretched films of poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) and its homopolymer polyvinylidene fluoride (PVDF) for comparison were investigated with the aim of understanding the electromechanical properties of this lower-modulus ferroelectric copolymer. The mechanical and the dielectric response at the glass transition ( relaxation) exhibit similar temperature dependence of the relaxation time, whereas mechanical and dielectric processes above the glass transition are not related. They represent a continuous softening process within the amorphous phase and the dielectric relaxation, respectively. The latter is attributed to conformational changes of VDF segments in lamellae of spherulites constituting the nonpolar crystalline phase. Furthermore, there is a contribution from melting of secondary crystallites formed in the amorphous phase during annealing or storage. Mechanically, this transition appears in nonstretched and stretched films as an accelerated decrease of the elastic modulus that terminates the rubber plateau. Dielectrically, this transition becomes visible as a frequency-independent loss peak only in stretched films, because stretching removes the relaxation, which superimposes the transition in nonstretched films. Melting of secondary crystallites is shown to appear in the homopolymer, too, though less pronounced because of more complete primary crystallisation. Stretching increases the modulus above the glass transition only slightly, and it does not significantly influence the softening process. On the other hand, stretching causes a spontaneous polarisation and introduces order within the amorphous phase, rendering it more polar. Melting of secondary crystallites provides an additional contribution to the polarisation. These findings may explain the relatively high electromechanical activity of P(VDF-HFP) but also its relatively low thermal stability. Moreover, they may be important for correct procedure and analysis of temperature-dependent dielectric measurements on partially crystalline polymers, in particular on those with less favourable sterical conditions for primary crystallisation. Y1 - 2012 U6 - https://doi.org/10.1007/s00339-012-6838-1 SN - 0947-8396 VL - 107 IS - 3 SP - 603 EP - 611 PB - Springer CY - New York ER - TY - JOUR A1 - Frübing, Peter A1 - Krüger, Harald A1 - Goering, H. A1 - Gerhard, Reimund T1 - Relaxation behaviour of thermoplastic polyurethanes with covalently attached nitroaniline dipoles Y1 - 2002 ER - TY - JOUR A1 - Frübing, Peter A1 - Kremmer, Alexander A1 - Neumann, Werner A1 - Gerhard, Reimund A1 - Guy, I. L. T1 - Dielectric relaxation in piezo-, pyro- and ferroelectric polyamide 11 N2 - Ferroelectric polyamide 11 films were prepared by melt-quenching, cold-drawing and electrical poling. Their ferroelectricity was studied by means of dielectric-hysteresis measurements. A remnant polarisation of up to 35 mC/m(2) and a coercive field of 75 MV/m were obtained. The piezoelectric d(33) coefficient and the pyroelectric coefficient of the films are reduced by annealing just below the melting region, but remain at about 3 pC/N and 8 muC/(m(2)K), respectively, during further heat treatment. Differential scanning calorimetry (DSC), dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarisation (TSD) were applied for investigating the conformational changes induced by melt-quenching, cold-drawing and annealing. The results indicate that the cold-drawn film mainly consists of a rigid amorphous phase which exhibits considerably lower conductivity, no glass transition and consequently no dielectric a relaxation. Instead, an a, relaxation is found, which is related to chain motions in regions of the rigid amorphous phase where the amide-group dipoles are not perfectly ordered. Annealing removes imperfectly ordered structures, but does not affect the ferroelectric polarisation. Therefore, it may be concluded that essentially the a, relaxation causes the thermally non-stable part of the piezo- and pyroelectricity in polyamide 11 Y1 - 2004 ER - TY - JOUR A1 - Frübing, Peter A1 - Kremmer, Alexander A1 - Gerhard, Reimund A1 - Spanoudaki, Anna A1 - Pissis, Polycarpos T1 - Relaxation processes at the glass transition in polyamide 11: From rigidity to viscoelasticity JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Relaxation processes associated with the glass transition in nonferroelectric and ferroelectric polyamide (PA) 11 are investigated by means of differential scanning calorimetry, dynamic mechanical analysis, and dielectric relaxation spectroscopy (DRS) in order to obtain information about the molecular mobility within the amorphous phase. In particular, the effects of melt quenching, cold drawing, and annealing just below the melting region are studied with respect to potential possibilities and limitations for improving the piezoelectric and pyroelectric properties of PA 11. A relaxation map is obtained from DRS that shows especially the crossover region where the cooperative alpha relaxation and the local beta relaxation merge into a single high-temperature process. No fundamental difference between quenched, cold-drawn, and annealed films is found, though in the cold-drawn (ferroelectric) film the alpha relaxation is suppressed and slowed down, but it is at least partly recovered by subsequent annealing. It is concluded that there exists an amorphous phase in all structures, even in the cold-drawn film. The amorphous phase can be more rigid or more viscoelastic depending on preparation. Cold drawing not only leads to crystallization in a ferroelectric form but also to higher rigidity of the remaining amorphous phase. Annealing just below the melting region after cold drawing causes a stronger phase separation between the crystalline phase and a more viscoelastic amorphous phase. Y1 - 2006 U6 - https://doi.org/10.1063/1.2360266 SN - 0021-9606 VL - 125 IS - 12 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Frübing, Peter A1 - Kremmer, Alexander A1 - Gerhard, Reimund A1 - Spannoudaki, Anna A1 - Pissis, Polycarpos T1 - Relaxation processes at the glass transition in polyamide 11 : From rigidity to viscoelasticity Y1 - 2006 UR - http://jcp.aip.org/ U6 - https://doi.org/10.1063/1.2360266 SN - 0021-9606 ER - TY - JOUR A1 - Frübing, Peter A1 - Grasnick, G. A1 - Herkner, G. A1 - Janietz, Dietmar A1 - Brehmer, Ludwig T1 - Pyroelektrische Untersuchungen an Polyvinylalkoholen mit Azobenzen / Alkoxy - Seitenketten Y1 - 1995 ER - TY - JOUR A1 - Frübing, Peter A1 - Blischke, D. A1 - Salah Khalil, M. A1 - Gerhard, Reimund T1 - Complete relaxation map of polyethylene : filler-induced chemical modifications as dielectric probes Y1 - 2001 ER - TY - JOUR A1 - Frübing, Peter A1 - Blischke, D. A1 - Salah Khalil, M. A1 - Gerhard, Reimund T1 - Dielectric relaxations in titanium-dioxide-filled polyethylene: Filler-induced chemical modifications of the polymer provide the dipolar response Y1 - 2001 SN - 0-7803-7053-8 ER - TY - JOUR A1 - Brehmer, Ludwig A1 - Frübing, Peter A1 - Herkner, G. A1 - Kaminorz, Yvette T1 - Pyroelektrische Untersuchungen an dünnen Schichten von organischen Seitenkettenpolymeren Y1 - 1995 ER -