Correlation Between Saturated Fatty Acid Chain-Length and Intermolecular Forces Determined with Terahertz Spectroscopy

08 January 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

We measured crystalline (C-form) saturated fatty acids with even carbon numbers ranging from 12 to 20 using temperature dependent terahertz time-domain spectroscopy (THz-TDS). Absorption features between 0.5 to 2.75 THz were identified at temperatures from 96 K to 293 K, and a systematic red-shift was obvserved with the increasing carbon chain length. The origins of these absorption bands were uncovered using state-of-the-art ab initio density functional theory (DFT) calculations. Similar vibrational motions in the absorption bands of the different materials highlight the unique role that THz-TDS has for probing weak non-covalent interactions in these materials. Our results showcase the utility of the terahertz region, which is beyond the scope of related vibrational techniques, providing direct evidence of the effect of chain length on the intermolecular interactions of these molecules.

Keywords

Terahertz spectroscopy data
Ab initio quantum chemistry methods
saturated fatty acids
Intermolecular forces

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