Comparative analysis of molecular interactions in PEG–ethanol, PEG–ethanol–epoxy, and PEG–ethanol–epoxy–TiO₂ systems at different temperatures for coating applications

• Comparative ultrasonic study of PEG-based coating formulations at 4 MHz • Fixed composition: 5% PEG-6000, 10% epoxy resin, 2% TiO₂ nanoparticles in ethanol • Temperature-dependent analysis conducted over 298–328 K • TiO₂ incorporation significantly enhances molecular packing and interaction strength • Ultrasonic parameters effectively predict coating performance and thermal robustness Ultrasonic methods can be used as a sensitive and non-destructive approach to investigate molecular interactions, structural features, and thermo-physical properties of complex multi-component liquid systems. In this study, a detailed comparative ultrasonic analysis has been conducted for three coating formulatons consisting of a constant 5% concentration of polyethylene glycol (PEG) as follows, (i) PEG and ethanol, (ii) PEG, ethanol, and epoxy, and (iii) PEG, ethanol, and epoxy reinforced with TiO 2 nanoparticles. Ultrasonic properties such as ultrasonic velocity, acoustic impedance, adiabatic compressibility, and free length of intermolecular interaction have been determined at a frequency of 4 MHz using an ultrasonic interferometer at four temperatures (298, 308, 318, and 328) K. In this way, a clear interaction hierarchy has been observed: PEG–ethanol < PEG–ethanol–epoxy < PEG–ethanol–epoxy–TiO₂. Acoustic insights strongly correlate with a wide range of coating performance indicators, which are adhesion, hardness, thermal resistance, and mechanical durability. The study concludes that 5% PEG–ethanol–epoxy–TiO₂ systems indeed represent the most promising characteristics for advanced coating applications where stability, strength, and functional performance have high demands. Ultrasonic characterization thus proves to be an effective predictive tool for optimizing polymeric and nano-composite coating formulations. Temperature elevation weakened interactions in all systems; however, the TiO₂-containing formulation preserved its superior structural stability even at higher temperatures, which showed its robustness.