Surface Excess Enthalpy of PEO + Salt +Water and L35 + Salt + Water Aqueous Two-Phase Systems

Abstract

Surface excess enthalpy, ∆H σ , associated with the interfacial formation process was determined at 298.15 K for five different aqueous two-phase systems (ATPS): L35Where L35 is one triblock copolymer denominated poly(oxide ethylene)-block-poly(oxide propylene)-blockpoly(oxide ethylene) with molar mass 1900 mol • g -1 and 50 % EO, PEO1500 is poly(oxide ethylene) with molar mass 1500 mol • g -1 and PEO4000 is poly(oxide ethylene) with molar mass 4000 mol • g -1 . The results show that the interface formation process could be exothermic or endothermic depending on the aqueous two-phase systems and/or tie line length (TLL), and its value is in the range of (-21.00 to 5.00) mJ. The ∆H σ measured was attributed a specific PEO-ion interaction associated with a polymer conformation change, both processes occurring at the interface phase. A significant effect of the electrolyte nature on the surface excess enthalpy was verified. Increasing the polymer size has an effect to release more energy for the ATPS interface formation process, while the substitution of PEO by L35, i.e, a hydrophobic increase on the top phase, makes more exothermic ATPS interface formation.

Microcalorimetric and SAXS Determination of PEO−SDS Interactions: The Effect of Cosolutes Formed by Ions

“…The only manner through which a salt could decrease γ is by specific interactions between the ions and the PEO segments. The adsorption and distribution of ions at interfaces of macromolecules/water is a fundamental process encountered in a wide range of biological and chemical systems . With PEO, it is recognized that the main interaction of PEO is with cations .…”

“…The adsorption and distribution of ions at interfaces of macromolecules/water is a fundamental process encountered in a wide range of biological and chemical systems. 38 With PEO, it is recognized that the main interaction of PEO is with cations. 39 However, Quina et al 40 followed the fluorescence quenching of free and polymer-bound chromophores by several salts (NaI, LiI, KI, NaSCN, LiSCN, and KSCN) in water and methanol.…”

Thermodynamic Study of Colorimetric Transitions in Polydiacetylene Vesicles Induced by the Solvent Effect

“…When thermal equilibrium between vessel and heat sink was reached, each solvent was titrated (1 μL) through a Hamilton microliter syringe at 60 min intervals. All calorimetric measurements were performed in triplicate, and the calculated relative standard deviation in the interaction enthalpy was on the order of ±0.5%. , …”

All-aqueous multiphase microfluidics

“…Alternatively, new ATPSs with interfacial tension higher than 10 À4 N/m and dynamic viscosity of less than 10 2 mPaÁs need to be investigated; this will increase the range of materials to meet the needs of the emerging applications using microfluidic technologies. Although such ATPSs have been found in systems composed of inorganic salts, 21,59 the concentrated salt solution phases are often too harsh an environment for proteins and cells, partly due to the inevitably high osmolarity. 1 Instead, ATPS composed of biocompatible macromolecules are promising alternatives that deserve further investigation.…”