Oxidation of polyacetylene in aqueous solutions containing sulphuric acid and selected supporting oxidants

Abstract It has been found that the addition of strong oxidants such as HNO 3 , NaNO 2 , KMnO 4 , K 2 Cr 2 O 7 and NaIO 3 to an aqueous solution of sulphuric acid greatly facilitates the insertion of HSO 4 − ions into (CH) x . [CH-(HSO 4 ) y ] x formation occyrs even in less concentrated solutions in which sulphuric acid alone does not oxidize polyacetylene. Based on the above observation, a new analytical method for NO 3 − determination has been proposed. The method consists of acidification of any neutral, aqueous solution of a nitrate salt with sulphuric acid to 5.7 M. Although H 2 SO 4 of such concentration does not oxideze polyacetylene, in the presence of NO 3 − , doping occurs due to the formation of free HNO 3 upon acidification. The doping reaction results in a significant increase of the electronic conductivity of the polyacetylene, σ. Log σ vs NO 3 − concentration plots are linear over a nitrate concentration range of 2 - 40 mM and can be utilized in chemical analysis. The selectivity of the proposed method is limited. Although the majority of common ions (HSO 4 − , Cl − , PO 4 3− , etc. …) do not influence the measurements, the presence of other (than HNO 3 ) oxidants in the solution must be avoided.