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

Abstract

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.

Inorganic and organometallic polymers

“…Thin films of poly(di-n-hexylsilane) absorbed on a poly(vinyl alcohol) substrate have been examined to determine the effect of film thickness on molecular orientation. 57 Polycarbosilane was grafted with poly(methyl methacrylate) (PMMA) or polystyrene (PS) to form random copolymers 23. 58 Molecular weights of the PMMA copolmers ranged from 17 000-19 000 g mol À1 (PDI = 2.1-5.0) whereas the styrene copolymers exhibited molecular weights from 13 000-20 000 g mol À1 (PDI = 2.2-2.6).…”

Molecular Thermal Hysteresis in Helix‐Dimer Formation of Sulfonamidohelicene Oligomers in Solution

“…Thermal hysteresis is a phenomenon in which different responses occur during heating and cooling. It is observed in condensed phases of solid states, [1] neat liquids, [2] bulk polymers, [3] or aggregates [4] (Figure 1). It is considered to be induced by strong and multiple cooperative interactions between molecules.…”