Pyrolysis Mass Spectrometry Analysis of BF₄⁻Doped Polythiophene

Abstract

Pyrolysis of electrochemically prepared BF 42 doped polythiophene (PTh) by direct insertion probe and Currie point pyrolysis gas chromatography mass spectrometry techniques indicated that thermal decomposition of PTh occurs in two steps. In accordance with literature results, the first step is assigned to the loss of the dopant, and the second step to the degradation of the polymer backbone producing segments of various conjugation lengths. At elevated temperatures, detection of products such as H 2 S and C 2 H 2 indicating cleavage of the thiophene (Th) ring was associated with a network structure. For the dedoped samples, a significant increase in the relative intensities of the peaks characteristic to the counter ion of the dopant, N(C 4 H 9 ) 4 þ pointed out the inward diffusion of (C 4 H 9 ) 4 N þ during the dedoping process.

Pyrolysis mass spectrometry analyses of poly(3-methylthiophene)

“…Taking also into account the single ion pyrograms of characteristic dopant-based products it can be concluded that inward diffusion of counter ion has occurred to balance the charge. This behavior was also detected for PTh sample but to a much lower extent [8,9]. Furthermore, the data also indicated evolution of oligomers at temperatures just above 200 8C, significantly lower than the degradation temperature of the polymer.…”

“…Recent pyrolysis studies on electrochemically prepared polypyrroles and polythiophenes showed that thermal decomposition products due to cleavage of the aromatic ring were more abundant contrary to the chemically prepared samples [7][8][9]13]. In general, it may be thought that the cleavage of the aromatic ring will be preferential only if the polymer has a network structure.…”

“…The dopant-based products were BF 3 , BF 2 , and BF, among which BF 2 gave the base peak. HF evolution was also significant in the same region and associated with reactions of dopant with water adsorbed on the polymer film during storage [8,9]. Peaks due to tributyl amine generated by decomposition of the counter ion of the dopant N(C 4 H 9 ) 4 + were present but quite weak indicating only a very limited adsorption of counter ion.…”

“…Application of pyrolysis mass spectrometry techniques for the structural analysis of polymers have been discussed in the literature in detail [11,12]. We have applied pyrolysis mass spectrometry technique for structural and thermal characterization of polythiophene, one of the most common conducting polymers, recently [7][8][9].…”

“…Although several studies on thermal degradation of polythiophene appeared in the literature [5][6][7][8][9], there are only few studies on thermal stability of PMTh [2,10]. The thermal stability of PMTh films electrochemically doped with SnCl 5 À and SbCl 6 À anions was studied by thermogravimetric analysis, TGA.…”