Correlation between structure and electrical conductivity of soluble polyphenylenes

Abstract

Polyphenylenes were prepared by using biphenyl-AICl3-CuC1, according to cationic oxidative polymerization. The chlorobenzene soluble fraction was doped with 10 O/o (w/v) solution of FeCI, in acetonitrile. The alternating electrical conductivity, X-ray diffractograms and the FTIR-spectra of both undoped and doped polyphenylenes were measured. The proportion of the components used for the preparation of polyphenylenes strongly influences their structure as well as their conductive properties. The undoped polyphenylenes were found to be insulators, but most of them became semiconductors after doping. The increase of the alternating electrical conductivity u' (resulting from the real part of the admittancevector) of the doped polyphenylenes has been explained considering the factors that influence the polyphenylenes structure: the high ratio of paralmeta, the presence of both amorphous and crystalline regions, and the presence of polynuclear structures. On the other hand, the presence of aliphatic structures interrupts the conjugation system, leading to lower u' values.

Synthesis and characterization of electrically conducting copolymers based on benzene and biphenyl

“…It is noticed that the spectra of the doped polyphenylenes exhibit the same absorption bands as those of the corresponding undoped. The various bands of the polyphenylenes were attributed to proper chemical bonds according to the literature4, 23, 29, 31, 34–37 and the results are summarized in Table II. The bands at 3030, 1600, 1480, and 1400 cm −1 are associated with the aromatic ring.…”

“…The broad absorption band at 1600 cm −1 is particularly strong if a further conjugation with aromatic rings takes place. The intensity ofthis band characterizes the degree of condensed aromatic rings in the case of polyphenylenes 4, 23, 29, 31, 34, 38, 39. The type of substitution can be obtained from the intense bands below 900 cm −1 .…”

“…In the case of the presence of the bands at 880–870 cm −1 , the stronger bands at 765 and 695 cm −1 can be attributed to meta ‐substitution. The presence of a small band at 740 cm −1 indicates ortho ‐substitution 4, 23, 31, 34…”

“…The structure of the different polyphenylenes under the aspect of their para‐ and meta‐ linkages can be estimated based on the intensity of the corresponding bands in the FTIR spectra. Specifically, the ratio of para‐ to meta‐ linkages ( R ) in the macromolecule can be determined from the ratio of the intensity of the band at 806 cm −1 ( I p ) to the sum of the intensities of the bands at 765 cm −1 ( $I_{m_1 }$ ) and 695 cm −1 ($I_{m_2 }$ ):4, 23, 29, 31, 34, 35 …”

“…Figure 1 shows the FTIR spectra of the undoped homopolymers H-PPP, H-PP-I and H-PP-S, whereas Figure 2 shows the FTIR spectra of the undoped copolymers C 1 -I, C 1 -S, C 2 -I, and C 2 -S. It is noticed that the spectra of the doped polyphenylenes exhibit the same absorption bands as those of the corresponding undoped. The various bands of the polyphenylenes were attributed to proper chemical bonds according to the literature 4,23,29,31,[34][35][36][37] and the results are summarized in Table II. The bands at 3030, 1600, 1480, and 1400 cm 21 are associated with the aromatic ring.…”