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Updated: Apr 14, 2026
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A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients
Published on: August 9, 2022
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Low-temperature phase transformation studies in the stearic acid: C form.
F F de Sousa1, P T C Freire2, A S de Menezes3
1Instituto de Ciências Exatas, Universidade Federal do Sul e Sudeste do Pará, CEP 68507-970 Marabá, PA, Brazil.
Summary
This study reveals a phase transition in stearic acid crystals at low temperatures using Raman scattering and X-ray diffraction. Structural changes continue down to 8 K, indicating complex low-temperature behavior.
Area of Science:
- Solid-state chemistry
- Materials science
Background:
- Stearic acid (C17H35COOH) is a long-chain fatty acid with various crystalline forms.
- Understanding its phase transitions is crucial for applications in materials science and condensed matter physics.
Purpose of the Study:
- To investigate the temperature-dependent phase transitions and structural changes in the C form of stearic acid at low temperatures.
- To characterize the vibrational and structural properties of stearic acid crystals under cryogenic conditions.
Main Methods:
- Polarized Raman spectroscopy from 8 to 300 K.
- X-ray diffraction (XRD) from 290 to 80 K.
- Differential scanning calorimetry (DSC) to identify thermal anomalies.
Main Results:
- Raman spectra indicated a phase transition between 210 and 170 K, with ongoing structural modifications down to 8 K.
- XRD measurements showed minor lattice parameter changes around 200 K.
- DSC detected an enthalpic anomaly near 160 K, confirming the phase transformation.
Conclusions:
- The C form of stearic acid undergoes a significant phase transition at low temperatures.
- Structural changes persist down to 8 K, suggesting complex low-temperature crystalline behavior.
- The study provides insights into the anharmonicity of vibrational modes and potential low-temperature space groups.
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