Deeply supercooled aqueous LiCl solution studied by frequency-resolved shear rheology

Area of Science:

• Physical Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Aqueous solutions of lithium chloride (LiCl) exhibit complex behavior near their glass transition.
• Understanding structural relaxation is crucial for characterizing the dynamics of ionic liquids and hydrogen-bonded fluids.

Purpose of the Study:

• To characterize the structural relaxation of aqueous LiCl solutions using frequency-dependent shear rheology.
• To confirm the generic spectral shape of glass formers in this hydrogen-bonded fluid.
• To validate the rheological equivalent of the Barton-Nakajima-Namikawa relation.

Main Methods:

• Frequency-dependent shear rheological experiments were performed near the glass transition temperature.
• Analysis was conducted within the fluidity representation.
• Mechanical response was compared with dielectric spectroscopy data.

Main Results:

• The generic spectral shape, previously observed in various glass formers, was confirmed for the aqueous LiCl solution.
• The rheological equivalent of the Barton-Nakajima-Namikawa relation was demonstrated to be valid.
• Comparison with dielectric spectroscopy revealed insights into coupled dynamics.

Conclusions:

• Aqueous LiCl solutions exhibit characteristic structural relaxation dynamics consistent with other glass-forming systems.
• Rheological and dielectric properties provide complementary information on molecular and ionic motion.
• The study contributes to understanding the viscoelastic behavior of ion-conducting liquids.