Solvent-Induced Changes in the Acoustic Parameters and Intermolecular Forces of Polyethene Glycol (PEG) Solutions

Abstract

The present investigation focuses on the influence of solvent polarity on the physicochemical and acoustic behaviour of polyethene glycol (PEG-400) solutions in acetone and dimethylformamide (DMF) at 300 K. Ultrasonic velocity, density and viscosity of PEG-400 solutions having different concentrations were experimentally determined using a single-frequency ultrasonic interferometer operating at 2 MHz, a calibrated specific gravity bottle and an Ostwald viscometer, respectively. The experimentally measured values were utilised to evaluate various acoustical parameters, namely adiabatic compressibility, intermolecular free length, acoustic impedance, relative association, ultrasonic attenuation coefficient and relaxation time. The variation of these parameters with polymer concentration was analysed to understand the nature of solute-solvent interactions.
The results reveal that ultrasonic velocity, density, viscosity and acoustic impedance increase progressively with increasing PEG concentration in both solvents, whereas adiabatic compressibility and intermolecular free length decrease systematically. These observations indicate enhanced molecular packing and stronger intermolecular interactions resulting from hydrogen bonding, dipole-dipole interactions and polymer-solvent association. The magnitude of these changes is considerably greater in dimethylformamide than in acetone because of the higher polarity and superior solvating ability of DMF towards PEG molecules. Linear regression analysis further demonstrates excellent agreement between the experimental observations and concentration-dependent behaviour of all measured parameters. The findings establish ultrasonic investigation as a reliable and sensitive technique for evaluating molecular interactions and structural organisation in polymer solutions and provide useful information for designing polymer-based systems employed in pharmaceutical, chemical and industrial applications.