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Solid-state low temperature→middle temperature phase transition of linoleic acid studied by FTIR spectroscopy
Fuwei Pi1, Fumitoshi Kaneko, Makio Iwahashi
1Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
The Journal of Physical Chemistry. B
|April 28, 2011
Summary
This study investigated the solid-state phase transition of linoleic acid using temperature-dependent FTIR spectra. The research found that the transition is localized around the cis-diene group, differing from oleic acid
Area of Science:
- Physical Chemistry
- Spectroscopy
- Materials Science
Background:
- Linoleic acid is a polyunsaturated fatty acid with two cis-double bonds.
- Understanding solid-state phase transitions is crucial for materials science applications.
- Fourier-transform infrared (FTIR) spectroscopy is a powerful tool for analyzing molecular structure and phase changes.
Purpose of the Study:
- To investigate the low-temperature (LT) to middle-temperature (MT) phase transition of linoleic acid.
- To elucidate the structural evolution of the acyl chain during this phase transition.
- To compare the transition behavior of linoleic acid with that of oleic acid.
Main Methods:
- Temperature-dependent FTIR spectroscopy was employed over a range of -80 to -30 °C.
- Band assignments were performed in the 900-760 cm(-1) region, focusing on cis-olefin and CH2 modes.
- The simple-coupled oscillator model was used to analyze progression bands and structural changes.
Main Results:
- The LT → MT phase transition in linoleic acid was observed and characterized.
- Structural changes were found to be localized around the cis-diene group.
- The conformational change during the LT → MT transition is less extensive than the γ → α transition in oleic acid.
Conclusions:
- The solid-state phase transition of linoleic acid is primarily localized around its cis-diene moiety.
- This transition differs significantly from the broader structural changes observed in oleic acid's γ → α transition.
- The findings provide insights into the molecular dynamics of polyunsaturated fatty acids in the solid state.
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