Thermodynamic
Properties of Polymorphs of 2,2′-Thiodiethylene
Bis[3-(3,5-di-<i>tert</i>-butyl-4-hydroxyphenyl)propionate]
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Abstract
In this work, two polymorphic forms
of 2,2′-thiodiethylene
bis[3-(3,5-di<i>tert</i>-butyl-4-hydroxyphenyl)propionate]
(abbreviated as TBHP) were successfully isolated, identified, and
characterized by using powder X-ray diffraction and differential scanning
calorimetry. It was found that form I has a lower melting temperature
than form II. The solubility data of both form I and form II of TBHP
in six pure solvents were experimentally measured in the temperature
range of (283.15 to 318.15) K at atmospheric pressure by using a dynamic
method. For all of the tested solvents, the solubility data of TBHP
form I are higher than those of form II. The modified Apelblat equation
was used to correlate the solubility of TBHP form I and form II. The
mixing Gibbs energy, the mixing enthalpy, and the mixing entropy of
both forms were also determined. It was also found that mixing processes
of both forms are endothermic, entropy-driven, and spontaneous. Combining
the DCS data and all of the thermodynamic data, it was concluded that
the relationship between form I and form II of TBHP is monotropic