A study of the structure and morphology of poly(p-phenylene) films electrosynthesized in liquid SO2 with different salts at low temperatures

Autor: P. Soubiran, Y. Pelous, Pierre-Camille Lacaze, Salah Aeiyach, G. Froyer
Rok vydání: 1995
Předmět:
Zdroj: Synthetic Metals. 68:213-219
ISSN: 0379-6779
DOI: 10.1016/0379-6779(94)02305-i
Popis: The structure and electrochemical properties of poly( p -phenylene) (PPP) films synthesized by oxidation of benzene in SO 2 were investigated by IR, UV, scanning electron microscopy and X-ray diffraction. In the presence of a Lewis acid (SbF 5 ) or boron trifluoride etherate complex ((C 2 H 5 ) 2 OBF 3 ), the potential of benzene oxidation is shifted to low values and the lowest potentials are obtained when the interaction between benzene and the acid (π-complex) is the strongest (1.6 and 1.1 V with (C 2 H 5 ) 2 OBF 3 and SbF 5 , respectively). As a general rule, the porosity of the PPP films decreases with temperature of synthesis, and their morphology depends on the synthesis conditions. They are amorphous with LiAsF 6 , but crystalline with other salts such as TBAX (X = BF 4 − , SbF 6 − ), with SbF 5 or(C 2 H 5 ) 2 OBF 3 . A hexagonal structure ( a = 11.5 A , c = 4.2 A ) is found with TBABF 4 (crystallite size around 150 and 200 A), and an orthorhombic system with TBASbF 6 ( a = 16.50 A , b = 13 A , c = 4.12 A ) or with SbF 5 ( a = 15.03 A , b = 11.25 A , c = 4.2 A ). The surface of the films is quite smooth in the presence of (C 2 H 5 ) 2 OBF 3 or LiAsF 6 and very rough with ammonium salts and SbF 5 . The homogeneity of the films, which is a volume property, is very good with films formed with LiAsF 6 or SbF 5 at −75 °C and is evidenced by n-doping in THF + TBABF 4 , which leads to a uniform blue colour on the whole surface. On the contrary, the homogeneity of films formed with (C 2 H 5 ) 2 OBF 3 is poor, and attested by the appearance of scattered blue stains by n-doping.
Databáze: OpenAIRE
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