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In the studied poly(tetrathiafulvalenes), PTTF, the TTF units are linked via phenyl groups or via tetrahydroanthracene bridges. The PTTF are doped with oxygen and with iodine respectively. The electrical conductivity strongly depends on temperature as it is typical of semiconducting materials. The existence of various types of paramagnetic centres is confirmed by ESR saturation experiments, by spectra simulation and by electron spin echo (ESE) measurements in the temperature region of 2 K to 400 K. At room temperature the doped PTTF have a dc conductivity between 10−9 Scm−1 and 10−4 Scm−1. Relations between the concentration of various radicals and the electrical conductivity of the polymers are discussed by means of a model based on mobile and immobile radicals, polarons and bipolarons. There are experimental indications for temperature‐dependent formation and break‐up of bipolarons which are discussed in the paper.

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Results of conductivity measurements on undoped and iodine or bromine doped poly(tetrathiafulvalenes) are reported. At higher temperatures the temperature dependence of the d.c. conductivity can be best described by σd.c. = °o. exp(T/To)1/4, typical for variable range hopping. The a.c. conductivity follows the general law °(ω) ∼ ω2 for frequencies higher than a critical frequency. A description of the frequency dependent conductivity is given by the extended pair approximation (EPA). At lower temperatures a deviation from linearity of the function in σ versus T−1/4 is observed.

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