Electrophysical Properties of Iodine Doped Acetylene/Ethylene Copolymers
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A.N.ALESHIN, E.G.GUK, V.A.MARIKHIN, L.P.MYASNIKOVA AND D.G.BELOV* A.F.Ioffe Physico-Technical Institute, Polytechnicheskaya 26, 194021 St.Petersburg, Russia * Institute of Chemical Physics, Chernogolovka, 142432, Russia
ABSTRACT A new oxydative-resistant, fusible and processible ethyleneiacetylene copolymer has been synthesized. The content of rigid (acetylene) and flexible (ethylene) fragments has been widely varied. The structure of the nascent powders and the films compressed at room temperature have been investigated by SEM and WAXS. DSC has been used for studying the thermal properties. DC conductivity of the iodine doped samples has been measured as a function of temperature. It is shown that the doping leads to arising conductivity in the samples even at 10 mol % acetylene fragments in copolymer. The conductivity up to 10-3 S/cm is reached for the samples with acetylene fragment concentration about 20 mol %. It is found that a charge carrier transport in investigated copolymers is caused by doped polyacetylene fragments and described by the hopping mechanism.
INTRODUCTION Much attention has recently been paid to a study of conjugated polymers which offer exiting potentialities for the new technology. Studies of polyacetylene (PA), the simplest conjugated polymer, have shown that the doped oriented PA samples have the dc conductivity close to the theoretical value - 105 S/cm [1]. PA, however has some disadvantages. It is unstable, infusible and insoluble, which makes it difficult to process it via conventional technology and limit its application. Recently, it has been shown that one of the promising route to solve this problem is to synthesize copolymers with flexible spacers between the rigid conjugated fragments [2]. The newly synthesized ethylene-acetylene copolymers have turned out to be oxydative resistant, fusible and soluble which makes this material very promising for practical use. The primary goal of this work was to investigate the structure of these copolymers and the dependence of the dc conductivity on their chemical nature. 273 Mat. Res. Soc. Symp. Proc. Vol. 328. ©1994 Materials Research Society
SAMPLES AND METHODS The ethylene-acetylene copolymers (EAC) have been synthesized using complex metalloorganic catalists Ziegler-Natta type [3]. The powder products of synthesis have been soluble, which pointed to their copolymer nature. The nascent powders of EAC have been intensively colored from light blue up to deep violet depending on the acetylene concentration in the initial gaseous mixture. The content of the acethylene fragments in the end products has been estimated by a flow gas of initial comonomers. The deep colour of the samples testifies to existence of long conjugated sequences. WAXS patterns have been taken using Cu ka radiation from the nascent powders and the films
compressed at room temperature. SEM micrographs (JSM-35) have been obtained for the nascent powders sputtered by Au. Thermal behavior has been studied by DSC (DSM-2). The samples has been doped by iodine both from va
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