Thermal Hysteresis and Thickness Dependence of the Molecular Orientation of Poly(di-n-hexylsilane) in the Film State

• Published in: The journal of physical chemistry. B 2006-05, Vol.110 (18), p.9072-9078
• Main Authors: Horiuchi, Hiroaki, Ishihara, Tomihiko, Tsunoda, Shin-ichi, Morishita, Daisuke, Takei, Tomoyuki, Okutsu, Tetsuo, Seko, Toshihiro, Sugino, Hiroaki, Kawakami, Yasuyuki, Watanabe, Hamao, Abe, Minoru, Takigami, Shoji, Hiratsuka, Hiroshi
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp0570566

Molecular orientation of poly(di-n-hexylsilane) adsorbed on poly(vinyl alcohol) film has been studied by making use of the stretching technique. Dichroic ratio, Rd, strongly depended on the thickness of poly(di-n-hexylsilane) thin film and the highest value ca. 19 was observed at the film thickness of 110 ± 30 nm. The thermal hysteresis of the molecular orientation was observed in the heating−cooling cycles. By studying the fluorescence spectrum it was confirmed that a portion of the poly(di-n-hexylsilane) molecules were in transoid conformation even at 320 K, although most of poly(di-n-hexylsilane) molecules were in disordered conformation (conformation D). This poly(di-n-hexylsilane) in transoid conformation is formed in the stretching process and may play a role of crystallization nucleus to induce the whole orientation of the poly(di-n-hexylsilane) in the film state.