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<p><i>γ</i>-CD·<i>n</i>H<sub>2</sub>O hydrates with different <i>n</i> have been investigated by powder X-ray diffraction analysis (PXRD), static method and differential scanning calorimetry (DSC). PXRD analysis of <i>γ</i>-CD·<i>n</i>H<sub>2</sub>O hydrates (<i>n</i> = 2.8–18.7) indicates the formation of two different structures depending on the water content. The PXRD patterns in the range of <i>n</i> from 18.7 to ≈ 12.5 correspond to the known literature structure of <i>γ</i>-CD·14.1H<sub>2</sub>O, while the diffractograms of <i>γ</i>-CD hydrates with lower water content suggest the formation of a different structure.The pressure of saturated water vapor of <i>γ</i>-CD·<i>n</i>H<sub>2</sub>O hydrates (<i>n</i> = 4.8–13.5) was measured by static method with membrane-gauge manometers in a wide range of pressure (240–88620&#xa0;Pa) and temperature (292–398&#xa0;K) under condition of a slight change in the solid phase composition. The phase transition was revealed at temperature <i>T</i> ~ 354&#xa0;K, and its enthalpy is calculated from static data and compared with the value determined by DSC data. The measured vapor pressure enlarges proportionally to the increase of the water content in the samples studied. Static experimental data (<i>p</i>(<i>T</i>)), being reduced to a single composition <i>γ</i>-CD·1H<sub>2</sub>O, were approximated by the equations ln<i>p</i>(1/<i>T</i>), which were used to compute the thermodynamic parameters of dehydration processes of the <i>γ</i>-cyclodextrin hydrates. The obtained equations (ln<i>p</i>(1/<i>T</i>)) permit to calculate the vapor pressure of water in <i>γ</i>-CD·<i>n</i>H<sub>2</sub>O hydrates within the studied temperature range for any <i>n</i> from 4.8 to 13.5. The information obtained was used to estimate Gibbs energy change during the binding of water to the <i>γ</i>-CD framework.</p>

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Thermal investigation of γ-cyclodextrin hydrates

  • 期刊论文

  • 发表日期：

    2026年1月22日

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  • L. N. Zelenina,
  • T. P. Chusova,
  • T. V. Rodionova,
  • Yu. D. Laventosa,
  • V. A. Rogov,
  • A. Yu. Manakov

摘要

γ-CD·nH2O hydrates with different n have been investigated by powder X-ray diffraction analysis (PXRD), static method and differential scanning calorimetry (DSC). PXRD analysis of γ-CD·nH2O hydrates (n = 2.8–18.7) indicates the formation of two different structures depending on the water content. The PXRD patterns in the range of n from 18.7 to ≈ 12.5 correspond to the known literature structure of γ-CD·14.1H2O, while the diffractograms of γ-CD hydrates with lower water content suggest the formation of a different structure.The pressure of saturated water vapor of γ-CD·nH2O hydrates (n = 4.8–13.5) was measured by static method with membrane-gauge manometers in a wide range of pressure (240–88620 Pa) and temperature (292–398 K) under condition of a slight change in the solid phase composition. The phase transition was revealed at temperature T ~ 354 K, and its enthalpy is calculated from static data and compared with the value determined by DSC data. The measured vapor pressure enlarges proportionally to the increase of the water content in the samples studied. Static experimental data (p(T)), being reduced to a single composition γ-CD·1H2O, were approximated by the equations lnp(1/T), which were used to compute the thermodynamic parameters of dehydration processes of the γ-cyclodextrin hydrates. The obtained equations (lnp(1/T)) permit to calculate the vapor pressure of water in γ-CD·nH2O hydrates within the studied temperature range for any n from 4.8 to 13.5. The information obtained was used to estimate Gibbs energy change during the binding of water to the γ-CD framework.