STUDIES OF THE THERMAL-DEGRADATION OF POLYTHIOPHENES BY PYROLYSIS-GASCHROMATOGRAPHY

The thermal degradation products of four polythiophenes were investiga ted by using pyrolysis-gas chromatography with a flame ionisation dete ctor (FID) and a sulphur-selective flame photometric detector (FPD). T he influence of pyrolysis temperature (550-1400 degrees C) and sample size (5-20 mu g) were studied, and the rates of formation and yields o f sulphur and hydrocarbons were determined. At low temperatures most o f the sulphur was found as H2S and the most abundant hydrocarbons were hexane and heptene. At high temperatures CS2 and C-1,C-2 hydrocarbons were formed secondarily. Only a very small amount of thiophenes was f ound. The ratio between the hydrocarbons changed somewhat with sample size, because of a change of the temperature gradient in the sample. R ates of formation for C-6 and C-7 hydrocarbons were the same for the d ifferent polythiophenes. The different chemical environment of the thi ophenic ring influenced the rate of formation of H2S and the yield of sulphur. The yields of the aromatic and thiophenic hydrocarbons were m uch less than aliphatics, because of a higher degree of carbonisation for the aromatic and thiophenic hydrocarbons.