Showing papers by "S. Roth published in 1985"
TL;DR: In this paper, the conductivity decrease of polyacetylene samples doped with iodine, AsF 5 and FeCl 3, respectively, and stored under various conditions (laboratory atmosphere, dry and humid air, vacuum, argon and argon at −30 °C) are reported.
10 citations
TL;DR: In this paper, the results of resonant Raman scattering experiments on trans-polyacetylene under hydrostatic pressure are reported, and the results show that the changes in the phonon frequencies are very small.
8 citations
TL;DR: In this paper, the far infrared transmission spectra of undoped cis and trans polyacetylene are reported in the frequency range from 30 cm-1 to 450 cm- 1.
7 citations
01 Jan 1985
TL;DR: In this article, an extension of these studies to other halogen molecules used as dopants of polyacetylene polymethyl methacrylate (CH)x has been presented, showing that both the near-edge structure and the extended fine-structure of the XA spectra yield a variety of information about the doping process and the orientation of the inserted halogen (poly-)anions with respect to the polyethylene chains.
Abstract: Despite of extensive investigations in the last few years, the structural properties of acceptor-doped polyacetylene are still in the midpoint of current debate /l/. This is due to the fact that the doping process leads to drastic changes of the relatively well-known structure of pristine (CH)x accompanied by a loss of long-range coherence and crystallinity. This limits the application of standard X-ray and neutron diffraction techniques. It has recently been demonstrated for the case of (CHBry)x that X-ray absorption (XA) studies can provide detailed information about the chemical form and local structure of the doped species /2,3/. In this contribution, we report on an extension of these studies to other halogen molecules used as dopants of (CH)x. We demonstrate that both the near-edge structure and the extended fine-structure of the XA spectra (called NEXAFS and EXAFS, respectively) yield a variety of information about the doping process and the orientation of the inserted halogen (poly-)anions with respect to the (CH)x chains. Stretch-oriented (CH)x samples, which represent quasi-one dimensional systems, were used in all investigations. This allows us to exploit the linear polarization of the synchrotron radiation (SR) in performing XA studies which are comparable with optical polarizer/analyser experiments.
6 citations
01 Jan 1985
TL;DR: In this paper, polypyrrole was polymerized electrochemically on a platinum electrode covered with a film of polyether/polyester elastomer and a black, conductive layer of polypoly(poly) poly(poly)-polymer was obtained.
Abstract: Polypyrrole was polymerized electrochemically on a platinum electrode covered with a film of polyether/polyester elastomer. Flexible films consisting of an elastomer layer and a black, conductive layer of polypyrrole were obtained.
4 citations
TL;DR: In this paper, specific heat and thermal conductivity of three types of polyacetylene samples are presented: (i) un-doped, (ii) highly conducting AsF5 doped, and (iii) (CH3)2NH compensated into the insulting state after asF5-doping.
Abstract: Data of specific heat and thermal conductivity of three types of polyacetylene samples are presented: (i) un-doped, (ii) highly conducting AsF5 doped, (iii) (CH3)2NH compensated into the insulting state after AsF5-doping. The specific heat of doped and undoped polyacetylene shows an anomalous behaviour below 1 K. Below 10 K the thermal conductivity of the compensated samples is higher than that of the doped samples and even much higher than that of the undoped ones.
3 citations
TL;DR: In this paper, the kinetics of polyacetylene doping by SbF5 IBr and I2 was studied by real-time neutron diffractometry, and the deviation from a Fickian behaviour obse...
Abstract: The kinetics of polyacetylene doping by SbF5 IBr and I2 was studied by real time neutron diffractometry. Fickian behaviour was observed for SbF5 and IBr. The deviation from a Fickian behaviour obse...
3 citations
TL;DR: In this article, the high-temperature spin kinetics of trans-polyacetylene in nitrogen and oxygen atmosphere are reported for 300 K T 550 K. The thermal reactions are characterized by S = 1/2 spin generation and annihilation processes.
Abstract: The high-temperature spin kinetics of trans-polyacetylene in nitrogen and oxygen atmosphere is reported for 300 K T 550 K. The thermal reactions are characterized by S = 1/2 spin generation and annihilation processes. ESR intensities and linewidths are analyzed.
2 citations
TL;DR: In this paper, high frequency AC (up to 10 THz) conductivity and short time photoconductivity (25 ps Illumination, 100 ps resolution) measurements are reported, interpreted as hopping between localized states and argued that due to a variety of imperfections of polymeric samples these states can not be identified, especially not as solitons.
Abstract: High frequency AC (up to 10 THz) conductivity and short time photoconductivity (25 ps Illumination, 100 ps resolution) measurements are reported. The conductivity is interpreted as hopping between localized states and it is argued that due to a variety of imperfections of polymeric samples these states can not be identified, especially not as solitons. In photoconductivity a fast transient, τ <100 ps, is observed and attributed to hot, non-thermalized carriers, followed by a ms tail, again due to hopping. The hopping origin of this tail is implied by the observation of similar experimental results in short-chain polyacetylene and in β-carotene.
1 citations
01 Jan 1985
TL;DR: Pulsed photoconductivity measurements in polyacetylene and s-carotene (an oligomer with eleven conjugated double bonds) are reported in this paper, where the lifetime of photoexcited carriers in these two systems is studied.
Abstract: Pulsed photoconductivity measurements in polyacetylene and s-carotene (an oligomer with eleven conjugated double bonds) are reported. Since both polyacetylene and s-carotene show light-induced conductivity, we have studied the lifetime of photoexcited carriers in these two systems. Some measurements were done in the picosecond regime to study the carrier motion before trapping,as well as in the micro- and millisecond regime to investigate the relaxation of carriers hopping between localized states. The experimental configuration is pointed out,and some of the difficulties connected with such experiments are discussed.