A study of the hydration of polyoxyethylene at low temperatures by differential scanning calorimetry

Abstract

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.

A study of the ageing of the gel structure in a nonionic O/W cream by X-ray diffraction, differential scanning calorimetry and spin-lattice relaxation measurements

“…In a series of papers [4][5][6][7] the results of research on the colloidal structures in a nonionic O/W cream and its separate components were discussed. The lamellar structure found in creams consisting of equal weights of cetylalcohol, stearylalcohol and PGM20, and containing 20 O/o/75 % w/w water, is depicted in Figure 3.…”

“…In samples of class II only the ratio of cetylalcohol and stearylalcohol was fixed (1 : 1 w/w). The amount of water was always large enough to ensure a complete basic hydration of the polyoxyethylene chains, which appeared to be two water molecules per oxyethylene unit [5,6]. In creams prepared for SLR measurements, 10 % of the water was replaced by D20.…”

“…In a series of papers [4][5][6][7] we discussed the colloidal structures present in 3-week-old samples of class I. Samples belonging to this dass are represented by the line indicated by d in Figure 2.…”

“…In a series of papers the gel structures present in nonionic O/W creams consisting of cetylstearylalcohol, poly(oxyethylene)20 glycerylmonostearate (PGM20) and water were discussed [4][5][6][7]. These creams may be considered as simplified versions of the O/W cream "Unguentum Hydrophilicum Nonionicum Aquosum", DAC [8].…”

“…These creams may be considered as simplified versions of the O/W cream "Unguentum Hydrophilicum Nonionicum Aquosum", DAC [8]. In order to elucidate the gel structures, results obtained by Differential Scanning Calorimetry (DSC, [5,6]), Small Angle X-ray Diffraction (SAXD, [4,7]), Wide Angle X-ray Diffraction (WAXD, [7]), Polarization Microscopy (PM, [7]) and Hectron Microscopy (EM, [7]) were combined.…”