Small-angle neutron scattering study of aqueous solutions of pentanediol and hexanediol

Abstract

Aqueous solutions of 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol and 1,6-hexanediol have been studied by small-angle neutron scattering over a wide range of concentrations and temperatures. The structure of the solutions on the mesoscopic length scale, corresponding to the intermolecular distances, was analysed with the help of the Kirkwood-Buff formalism. 1,2-Hexanediol solutions exhibited a strong attractive diol-diol interaction, a weak diol-diol attraction was found for 1,6-hexanediol and 1,2-pentanediol, and an extremely weak diol-diol attraction was found in 1,5-pentanediol solutions. The general tendencies are the following: aggregation is stronger as the length of the hydrophobic hydrocarbon chain increases and the 1,2-diols exhibit much stronger attraction then the 1,ω-diols. The temperature dependence of the aggregation is weak for the 1,2-diols but strong for the 1,ω-diols, indicating in the latter case the hydrophobic character of the interaction. © International Union of Crystallography 2007.