Ultrasonic Investigation of Molecular Interactions in Dextran–Aqueous NaOH System at Different Temperatures

Utilizing ultrasonic techniques at a fixed frequency of 1 MHz, this study examines the molecular interactions and acoustic properties of the high molecular weight polysaccharide Dextran (Mw 70,000) dissolved in aqueous 1(M) NaOH at different concentrations (0.1%, 0.25%, 0.5%, 0.75%, and 1% w/v) and temperatures (303 K, 308 K, 313 K, 318 K, and 323 K). Important acoustical and thermodynamic parameters, such as acoustic impedance (Z), adiabatic compressibility (β), intermolecular free length (L f ), relaxation time (τ), and Gibbs free energy for molecular interaction (ΔG), were calculated using the experimental measurements of ultrasonic velocity, density, and viscosity. These results offer important new information about Dextran's conformational behavior, solvation dynamics, and interaction mechanisms in a highly basic aqueous medium. The study provides a better understanding of molecular relationships in intricate biopolymer solutions and demonstrates the usefulness of ultrasonic techniques in characterizing polymer–solvent systems.