THERMAL-ANALYSIS OF FECL3-DOPED POLY(3-BUTYLTHIOPHENE) AND POLY(3-DODECYLTHIOPHENE)

For neutral and FeCl3-doped poly(3-butylthiophene) (P3BT) and poly(3-dodecylthiophene) (P3DDT), conductivity measurement and thermal analysis are performed. Before doping, the glass transition temperatures (T(g)) of the P3BT and P3DDT are 75.4-degrees-C and 5.6-degrees-C respectively. No melting transition of an ordered phase for P3BT is observed. But for P3DDT, the melting temperatures of ordered side chains and main chains are 56.1-degrees-C and 116.3-degrees-C respectively. Upon doping, the T(g)'s shift upward to 150.5-degrees-C and 51.2-degrees-C for P3BT and P3DDT respectively and the two melting peaks of the ordered phases of P3DDT disappear. The dopant anions decompose in the range of about 150 to 230-degrees-C. The conductivities increase with increasing temperature and reach maxima at 135-degrees-C and 28-degrees-C and drop sharply in the range of 160-200-degrees-C and 130-170-degrees-C for P3BT and P3DDT respectively. This indicates that the thermal motion of the main chains would lead to a drop of conductivity due to thermal undoping, while the dopant decomposition would lead to a rapid loss of conductivity and an occurrence of crosslinking reaction.