The interest of the scientific community for a better understanding of the static and dynamical properties of complex liquids in both bulk confinement and at the interface is driven by the need to control and design the structure and functionality of various biomolecules and develop new diagnostic protocols. Glycerol, a viscous cosolvent, forms three hydrogen bonds with water molecules. Glycerol-water associates participate in dynamic functional networks that serve as a sound system for modeling H-bonding in biological systems. Glycerol-water mixtures, a widely used medium with a broad range of viscosities, have various applications, such as stabilizing enzyme activity and protein structures. Protein flexibility and structure preorganization define the hydration of different sizes of proteins (20-100 Å) occurring on various length scales (0.3-10 Å), and water-glycerol mixtures' behavior at such length scales is critical. Thus, it is necessary to perceive the rheological and structural properties of both these mixtures alone and in the presence of protein molecules. The structural changes are accompanied by functional changes in electron and ion-transport, which have been studied by molecular dynamic simulations, broadband dielectric spectroscopy, and neutron scattering.<br/>This work aims to differentiate between these structures in water-glycerol mixtures and reveal differences in bulk (protein folding) and viscous interactions (hydration and local rotation). We are demonstrating continuous probing of length scales from bulk to nanometer by using three complementary acoustic techniques. This multimodal approach is based on the shear-mode quartz crystal microbalance (QCM-D) principle for measuring, in dissipation mode, highly viscous liquids, and we access nine odd-harmonics along with the fundamental (5-85 MHz). Also, we apply high-resolution ultrasonic spectroscopy (HR-US), which employs high-frequency (1-20 MHz) waves of longitudinal deformations and small-amplitude oscillatory shear rheometry (SAOS). HR-US and SAOS probe the liquid's bulk properties, whereas QCM-D depending on the odd-harmonic and, therefore, the shear waves' penetration depth, probes both bulk and interfacial properties. The acoustic measurements will be correlated with literature results from impedance spectroscopy and neutron scattering to enable the coupling of acoustic and electrical spectroscopy for the multifunctional, viscoelastic characterization of complex liquid mixtures.

Multimodal and multifunctional characterization of complex liquids: – From bulk to interface

ACS Spring Meeting 2021

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