Effects of Size, Shape, and Polarity of Components in the Binary Mixture of Ionic Liquid ([C₄mim][Cl]) and Cyclic Ether ((1,4-dioxane)) on Speed of Sound at Different Temperatures

Abstract

The molecular size, shape, and polarity of ionic liquids (ILs) and cyclic ethers significantly influence the acoustic and thermodynamic properties of their binary mixtures. This study investigates the variation in the speed of sound in IL–cyclic ether binary mixtures as a function of temperature (298–328 K) and composition. The ionic liquid 1-butyl-3-methylimidazolium chloride ([C₄mim][Cl]) was mixed with the cyclic ether (1,4-dioxane). Speed of sound measurements were performed using an ultrasonic interferometer. Results demonstrate that structural parameters and dipole interactions affect compressibility and, consequently, the speed of sound. Stronger hydrogen bonding and denser packing led to higher values at lower temperatures, while temperature rise generally decreased sound velocity due to reduced interaction strength. The findings provide insights into molecular-scale interactions and their impact on bulk acoustic behavior.