A study of the hydration of polyoxyethylene at low temperatures by differential scanning calorimetry |
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| Authors: | T de Vringer J G H Joosten H E Junginger |
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| Institution: | (1) Department of Biophysics, Physics Laboratory, Utrecht University, Utrecht, The Netherlands;(2) Division of Pharmaceutical Technology, Center for Bio-Pharmaceutical Sciences, Leiden University, Leiden, The Netherlands;(3) Present address: Gorlaeus Laboratories, P.O. Box 9502, 2300 RA Leiden, The Netherlands |
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| Abstract: | As a part of a study of the colloidal structures present in nonionic ointments, the interaction between polyoxyethylene and water is investigated. A series of mixtures of polyoxyethylene 1550 and water is studied using differential scanning calorimetry. Heating as well as cooling experiments are performed. The effects of the heat of mixing, supercooling and melting point depression on the measured enthalpy changes are discussed. From the non-freezing water fraction it is concluded that 2 water molecules per oxyethylene unit are tightly bound to the polymer chain. The observed differences between the cooling and the heating curves lead to a possible explanation for the alterations in the samples occurring at low temperatures. A hydrate structure of polyoxyethylene at low temperatures is proposed. Finally, comment is made on the phase diagram of the system polyoxyethylene/water. |
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| Keywords: | Polyoxyethylene DSC water structure |
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