Autooxidation and stabilization of undoped and doped polyacetylenes

Abstract

Abstract Autooxidations of polyacetylene have been measured by volumetric, infrared, and isothermal TGA weight uptake techniques. The rate of oxygen uptake is 9 × 10 −7 mol (g s) −1 at 70°C and the overall activation energy is about 10 kcal mol −1 . The maximum oxygen uptake corresponds to [CHO 0.25 ] x . Above 100°C there is oxidative degradation of the polymer completely to volatile products. The rate constant for the oxidative degradations at 160°C is ca. 1.5 × 10 −5 s. Autooxidation does not result in formation of significant amounts of crosslinking because there are not carbonaceous residues. TGA under a stream of oxygen showed the degradation to be complete at ca. 420°C leaving no residues. Autooxidation is much slower if the polymer is compressed to higher bulk density. Radical scavengers such as BHT and 4010 are effective stabilizers. Hydroperoxide decomposers, such as DSTDP, does not help in the stabilization; spin trap BPN accelerates the oxidation of polyacetylene. Iodine and AsF 5 doped polyacetylenes are oxidatively much more stable than undoped polymers. Perchlorate doped polyacetylenes begin to lose weight as soon as heated above room temperature. Even in an inert atmosphere the polymers often undergo explosive decomposition.