Correspondence between Spectral-Derived and Viscosity-Derived Local Composition in Binary Liquid Mixtures Having Specific Interactions with Preferential Solvation Theory.

Local interactions between unlike molecules (1-2) in solution are commonly measured with spectroscopy and used to estimate local composition. Herein, a viscosity model based on preferential solvation (PS) theory is developed for aqueous and nonaqueous binary liquid mixtures containing a dipolar aprotic solvent that provides local composition considering the hydration or solvation shell around complex (1-2) molecules. Spectral-derived and viscosity-derived local composition distributions showed similar trends with bulk composition, and their correspondence is attributed to characteristics of the hydration or solvation shell.

Analysis of the Cybotactic Region of Two Renewable Lactone-Water Mixed-Solvent Systems that Exhibit Synergistic Kamlet-Taft Basicity.

Kamlet-Taft solvatochromic parameters (polarity, basicity, acidity) of hydrogen bond donor (HBD)/acceptor (HBA) mixed-solvent systems, water (H2O)-γ-valerolactone (GVL), methanol (MeOH)-GVL, ethanol (EtOH)-GVL, H2O-γ-butyrolactone (GBL), MeOH-GBL, and EtOH-GBL, were measured over their entire composition region at 25 °C using UV-vis spectroscopy. Basicity of H2O-GVL and H2O-GBL systems exhibited positive deviation from ideality and synergism in the Kamlet-Taft basicity values. The cybotactic region around each indicator in the mixed-solvent systems was analyzed with the preferential solvation model.

Spectroscopic Analysis of Binary Mixed-Solvent-Polyimide Precursor Systems with the Preferential Solvation Model for Determining Solute-Centric Kamlet-Taft Solvatochromic Parameters.

Hydrogen bond donor/acceptor mixed-solvent systems for solutes that exhibit strong specific interactions are not readily characterized with methods that depend on solvatochromic parameters. In this work, the reaction of two monomers, 4,4′-oxidianiline (ODA) and pyromellitic dianhydride (PMDA), to form the common engineering plastic precursor, poly(amic acid) (PAA), are studied for the tetrahydrofuran (THF) mixed-solvent systems (THF-methanol, THF-ethanol, THF-water) with spectroscopy. Solute-centric (SC) Kamlet–Taft solvatochromic (K-T) parameters for the solvent environment around the monomer are determined using a proposed model that incorporates spectroscopically determined local composition (X(L)) around the ODA monomer and the preferential solvation model.