Exploring molecular interactions in two aqueous alkanolamines mixtures using refractive indices and molecular probes

Abstract

The optical and solvatochromic properties of aqueous mixtures of two alkanolamines (2-(ethylamino)ethanol and 2-(isopropylamino)ethanol) promising candidates to CO2 capture were investigated to better understand the changes in structural characteristics of the aggregation patterns formed throughout the whole composition range. The maximum absorption wavelengths of four molecular probes at T/K = 298.15, and refractive indices at T/K = (283.15 to 303.15) were measured. Solvent polarity descriptors (ETN30, ETN33, π*, α and β) and the corresponding mixing functions were derived. Molar refractions were calculated, and for the first time, excess molar refractions were estimated based on the recently derived refractive index of the ideal mixture. The correlation between excess refractive indices and excess molar volumes was explored, shedding light on the different ranges where changes in aggregation patterns are operating. Interesting insights on solvent polarity and structural details across the entire composition range were gained.