Influence of ionic and polymer composition on the properties of the phases of aqueous two-phase systems formed by non-ionic polymers

Abstract

Partitioning of a homologous series of sodium salts of dinitrophenylated amino acids with aliphatic side-chains in aqueous dextran—poly(ethylene glycol), dextran–polyvinylpyrrolidone and dextran–Ficoll two-phase systems of different polymer concentrations and various ionic compositions was studied. The differences in the abilities of aqueous media in the coexisting phases of the systems used to participate in ionic and hydrophobic hydration interactions with a partitioned solute are estimated. The hydrophobic hydration ability appears to depend mostly on the polymer composition of the phases, while the ionic hydration ability is governed mostly by the ionic composition. In particular, it is found that the ionic hydration and hydrophobic hydration abilities of water are interrelated. Both these characteristics of water in the two phases are considered with regard to the distribution of hydrogen-bond strengths and the relative stability of the hydrogen-bond networks in the phases.