Investigation of the Effect of Dopant on Characteristics of Poly(3‐methyl thiophene) via Pyrolysis Mass Spectrometry

Abstract

In this work, a direct insertion probe pyrolysis mass spectrometry technique was applied to investigate the thermal and the structural characteristics of electrochemically prepared PF6 − and BF4 − doped poly(3‐methylthiophene) (PMTh) to explore the effect of dopant on thermal and structural characteristics. It has been determined that the thermal degradation of PMTh occurs in two steps as in the case of polythiophene, (PTh). The first step was assigned to the loss of the dopant, and the second step to the degradation of the polymer backbone producing segments of various conjugation lengths. Generation of some oligomers occurred at lower temperatures for PF6 − doped films compared to BF4‐PMTh. On the other hand for both PMTh samples products due to the degradation of thiophene ring were detected in the same temperature range. Evolution of dopant based products occurred in a broad temperature range for both PF6 − and BF4 − doped poly(3‐methylthiophene). Reactions of dopants with H2O and polymer were very effective, especially for PF6 − and substitution of thiophene ring was noted for both samples. Decomposition of the polymer and inward diffusion of counter ion during dedoping processes of both polymers pointed out that electrochemical reversibility of the transition between the doped and undoped states is limited for PMTh.