Investigation of Undoped and Alkali-Metal Doped Poly(p-phenylene Selenide)
In the last few years, conducting polymers with non-degenerate ground state and with conductivity mechanisms somewhat different from the case of transpolyacetylene have attracted strong interest. Polaron-type defects in these polymers (Polyparaphenylene (PPP), Polypyrrole (PP), Polythiophene (PT), Polyparaphenylene sulfide (PPS)) leading to the presence of quinoid structure segments, have been theoretically predicted  and are expected to depend on the presence of impurities  as well as on the chain length of the polymer . Another polymer with a non-degenerate ground state is polyparaphenylene selenide (PPSe) which was investigated up to now only incidentally [4,5]. Moreover, investigations on the electronic structure of PPSe have not been reported up to date. It is known  that polyparaphenylene sulfide doped by strong p-dopant molecules has a rather high conductivity (∿1 S/cm). Substitution of sulfur by selenium may be favourable for high conductivity due to the increased metallic character of selenium and due to a decrease in electronegativity. Moreover, there is experimental evidence [7,8] that doped selenium compounds have higher conductivities than similar sulfur systems. However, also opposite results were reported . In this contribution we have used electron energy loss spectroscopy and electron diffraction to investigate the electronic and crystal structure of undoped and doped PPSe.
KeywordsSulfide Benzene Argon Selenium Oligomer
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