Mechanism of polyalcohol solid—solid phase change

TL;DRAbstract

Many polyalcohols will change from one crystal structure to another at certain temperatures. A lot of works had reported their phase change enthalpy, phase change temperature and phase diagram. It is taken that their phase change enthalpy must be related to their hydrogen bond. This article investigated quantitatively the relation between phase change enthalpy and hydrogen bond of NPG (neopentylglycol), PG (pentaglycerino) and PE (pentaerythritol) on the basis of infrared spectrum experimental data and calorimetric results. It was shown that before phase change, all the —OH are associated and as a result NPG, PG and PE form layer structure. After phase change, NPG, PG and PE move along the layer and as a result some hadrogen bonds break. Therefore the phase change enthalpy equals the energy used to break hydrogen plus the energy used to increase the vibration frequency of other still associated —OH.

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