Conformational changes of poly(3-alkylthiophene)s with temperature and pressure

• Published in: Synthetic metals Vol. 63; no. 2; pp. 101 - 108
• Main Authors: Iwasaki, Ken-ichi, Fujimoto, Hitoshi, Matsuzaki, Susumu
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 31.03.1994; Amsterdam Elsevier Science; New York, NY
• Subjects: Applied sciences; Electrical, magnetic and optical properties; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Solid state; Electrical conductivity; Pressure effect; Electrical properties; Thiophene derivative polymer; Optical properties; Electrical conductor; Experimental study; Thermochromism; Conformational transition
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/0379-6779(94)90256-9

Thermochromism of cast films of poly(3-hexylthiophene) and poly(3-dodecylthiophene) was studied by electronic absorption and FT-IR spectra. A possible mechanism for the transition is discussed from the viewpoint of conformational changes of the methylene side chains deduced from the FT-IR spectra. Electronic absorption and vibrational spectra of poly(3-hexylthiophene) films were measured at high pressures by use of a diamond anvil cell. The absorption edge energy decreased with increasing pressure up to 3 GPa and then showed leveling off and subsequent increase. The decrease is probably due to an increased conjugation length of the thiophene main chain caused by a compact packing of methylene side chains. On the other hand, the increase in the edge energy is attributed to a distortion of a plane polymer structure caused by the steric hindrance between neighboring polymer chains. Electric conductivity of a poly(3-hexylthiophene) film showed the pressure dependence parallel to that of the absorption edge.