A calorimetric investigation of interactions in aqueous solutions of poly(oxyethylene), 1. Heats of mixing of oligomeric models

Abstract

Heats of mixing with water as function of the composition of the mixtures for oligomeric models of poly(oxyethy1ene) at 25°C are reported, i.e. for compounds of the type XO(C%CH,O),,X (where X = H or CH, and n = 1, 2, 3, or 4) and CH30(CH2CH20),,,H (where m = 1 or 2). These dependencies greatly depend on the character of the end groups and on the degree of oligomerization. A procedure has been suggested for the comparison between the heat of mixing of longer chains and that of shorter ones with elimination of the effect of end groups. On the same mass basis, longer chains release more heat than shorter ones in mixing with water for concentrated solutions; hence, one may assume some kind of cooperativity of ether oxygen atoms in the same chain by hydration.

Phase Equilibria in Binary Mixtures of Water with Triglyme and Tetraglyme: Experimental Determination and Thermodynamic Modeling

“…more accurate method using differential heat capacity measurement by the Picker microcalorimeter. Figure4shows an almost perfect accord between extensive experimental excess enthalpy data available for the (water + G4) system (data of Birošet al12 at 298.15 K and those of Krumbeck and Schulz 13 at six temperatures from 298.15 to 448.15 K) and respective H E (x 1 ) curves calculated by the extended SSF model.…”

“…The graphical illustration of the fits of the thermal data is shown in Figures 3 and 4. As seen in Figure 3 for the (water + G3) system, the H E (x 1 ) and C p E (x 1 ) data selected for the correlation, measured at 298.15 K accurately by Birošet al 12 and Schrodle et al, 15 respectively, are captured perfectly. On the other hand, the C p E data of Mundhwa et al 25 (not involved in the correlation database) are seen to be appreciably deviating from both Schrodle et al's data and the fit and also considerably scattered.…”

“…Apart from the present water activity data obtained at two temperatures, the databases for the correlations comprised classical excess enthalpy data H E (x 1 ) covering the whole composition range, 12,13 dissolution enthalpies of glymes at infinite dilution in water Δ sol H 2 ∞ obtained by specialized calorimetric measurements, 14 and in case of G3, also excess heat capacity data C p E . 15 The adjustable parameters of the model were evaluated by the weighted least squares method minimizing the objective function…”

Dynamic properties of aqueous solutions of ethylene glycol oligomers as measured by the pulsed gradient spin-echo NMR technique at 25[deg ]C

“…Concerning the solventÈsolute interactions, in the literature it has been noted, on the same mass basis, that longer chains release more heat than shorter ones in mixing with water for concentrated solutions.34 Hence, one may assume some kind of synergism among the various ethoxy groups present in the same chain by hydration. 34 Kjellander and Florin35 suggested cooperation of the water molecules hydrating neighbouring sites. This e †ect has to be expected in the dilute region.…”

A thermoanalytic method for the study of the solubility of polyethylene glycols in ethanol and water

“…From the technical point of view the macroscopically homogeneous solution is most important even if it is not a completely molecular-dispersed solution [3]. It is evident that such a "technical solubility" cannot be defined by a sharp solubility limit due to high viscosity of the solution and supersaturation.…”