Hydration studies on some polyhydroxy non-electrolytes and non-ionic surfactants

Abstract

The hydration numbers of some polyhydroxy non-electrolytes and polyoxyethylenated non-ionic surfactants have been determined and found to depend considerably on the method used, the general order being conductometry < ultrasonic interferometry < ir, spectrophotometry. PEG and Tx-100 are exceptions to this trend. The results from ultrasonic interferometry study strongly depend on the data treatment. The maximum hydration obtained using the ir method shows fair agreement with recent nmr and low angle light scattering results on similar compounds. The results indicate the existence of both strongly and loosely bound water molecules with the micelles as well as the penetration of water in the non-polar micellar region.Key words: hydration, non-electrolytes, non-ionic surfactants, conductometry, ultrasonic, near infrared. Chem. 67,356 (1989).On a determink les nombres d'hydratation de quelques composCs non-tlectrolytes polyhydroxylCs et de quelques agents de surface non-ioniques polyoxyCthylCnCs et on a trouvC que ces valeurs dipendent grandement de la mCthode utiliske pour les dkterminer et que I'ordre gCnCral est le suivant : conductimCtrie < interfCromCtrie ultrasonique < spectrophotomCtrie ir. Le PEG et le Tx-100 sont des exceptions a cette tendance. Les rksultats obtenus a l'aide de I'interfCromCtrie ultrasonique dkpendent beaucoup de la f a~o n dont les donnCes sont traitCes. L'hydratation maximale qui est rtalisCe par la mCthode ir prksente une bonne corrClation avec celle obtenue rtcemment par rmn et par diffusion de la lumiere sur des composCs semblables. Les rCsultats suggerent l'existence de molCcules d'eau tant fortement que faiblement liCes aux micelles ainsi que la pCnCtration de l'eau dans la region non-polaire de la micelle.Mots clbs : hydratation, non-Clectrolytes, agents de surface non-ioniques, conductimCtrie, ultrasonique, infrarouge proche.[Traduit par la revue]Ions and non-polar molecules interact with water so that the molecules of the latter get attached to the former, lose their identity from the bulk water and ultimately yield separate kinetic entities. Polyhydroxy compounds readily hydrate and non-ionic surfactants with polyhydroxy groups are solubilised in water through hydration at their available hydroxy centres. The outer mantle of the micelle is protected through hydration, their microscopic properties such as catalysis, local viscosity, solubilisation etc. are functions of hydration and the vicinal water structure. In our effort to characterise micelles and polyhydroxy compounds in aqueous medium we have been interested in their hydration behaviour (1, 2). Informations on small hydroxy non-electrolytes are available but those on relatively large molecules are rather meager. Different methods (3-6) such as viscosity, diffusion, light scattering, etc. have been mostly used for this purpose. Nuclear magnetic resonance studies (7, 8) have also been found suitable. We have used conductometry, ultrasonic interferometry, and near-ir spectrophotometry as experimental approaches. In some recen...

Physicochemical studies on the biopolymer inulin: A critical evaluation of its self‐aggregation, aggregate‐morphology, interaction with water, and thermal stability

“…Subtracting the specific volume of the anhydrous inulin (reciprocal of density, ρ inulin = 1.328 g/ml) from the V h (2.12 ml/g) produced hydration of inulin = 1.37 ml/g. From this, the mole of water bound per mole of O‐atom in the polymer (five O‐atom per repeating unit of inulin) was estimated to be 2.47 mol/mol of O‐atom, which was in agreement with the literature value 53. The V h was estimated without assuming any shape of the polymer.…”

Physicochemical Investigation of Biocompatible Mixed Surfactant Reverse Micelles: III. Aqueous NaCl Solubilization, Thermodynamic Parameters of Desolubilization Process and Conductometric Studies

“…From Table 5, it can be observed that DH 0 s more exothermic in mixed DOSS/nonionics (X STO20EO or SMO20EO = 0.05) systems compared to single DOSS system in these oils. The greater solvation of polyoxyethylene head group of STO20EO or SMO20EO (compared to DOSS) [52] may contribute an exothermic share to the overall thermal events, making the resultant enthalpy of water solution more exothermic with mixed DOSS/STO20EO or SMO20EO systems. On the other hand, DOSS/SMO20EO system makes a larger exothermic contribution towards the water dissolution process compared to DOSS/STO20EO systems at comparable conditions.…”

Subzero Temperature Behavior of Water in Microemulsions

“…In addition, the 10 EO groups may form one coil [155], within which water may be caged. The measured molar ratio of bound water to EO group, N W/EO , was 4.42 when the hydrophobic residue was monolaurate, increasing to N W/EO ϭ 6.07 for monostearate and to N W/EO ϭ 8.84 for monooleate [169]. Even if we assume that Brij 97 is not able to form such a definite structure in the four-component system B, the surfactant still has one more way of stabilizing the system that is not applicable to polyethylene oxide.…”