Interchain vibrational coupling in phase II (hexagonal) <i>n</i>-alkanes

Abstract

The intense methylene scissoring and rocking bands near 1460 and 720 cm−1 in the infrared spectra of the odd n-alkanes C17–C27 show doubling in phase II, the so-called hexagonal phase. This doubling, which is shown to be due to interchain vibrational coupling, is highly dependent on temperature and chain length. A possible explanation for this dependency is offered in terms of a combination of static and dynamic factors associated with more or less constrained rotational/twisting motions of the chains about their long axes.