Supercooled liquids are liquids which have been placed in a temperature below the liquids freezing point, but are not in a solid state. They appear to solidify, but in reality have a very viscous structure and flow under the influence of any external unbalanced forces, like gravity. They can be under freezing point, and still not crystallize. They are used in everyday appliances like your refrigerator. An example that clearly reflects the characteristics of a supercooled liquid is hot glass, which is malleable, and eventually acts like a solid, but it is technically an extremely viscous liquid. That is why, that is why even though appearing solid, when its structure is disturbed, like when it is dropped, it shatters because the molecular charges repel.
Now for shear thinning that supercooled liquid. Shear thinning is the name for an the behavior of fluids whose viscosity decreases under shear strain. One example would be when the shear created by the brush or roller will allow the paint to thin and wet out the surface evenly. Once applied, the paints regain their higher viscosity, which avoids drips and runs, effectively acting as a solid. Shear strain is much less complicated than it sounds. We can define shear strain in the same way as longitudinal strain: the ratio of deformation to original dimensions. However, for Shear Strain it’s the amount of deformation perpendicular to a given line rather than parallel to it. Imply put for the purposes of this article, it is a type of deformation that changes the geometric shape of a certain object, which in this case is the circular molecular structure of supercooled liquids. Initially, as a supercooled liquid is made to flow by shearing, its viscosity remains unchanged. But as the liquid is flowing faster, it becomes less gooey meaning the viscosity starts to decrease. This process is an example of the phenomenon mentioned above. In fact, shear thinning is used industrially in something as simple as when two lubricated surfaces slide against each other. However, one of the most intriguing topics to physicians os supercooling because they do not know the mechanism behind this process.
Certain researchers used computer simulations to simulate the shear cooling process on supercooled liquids. The sheared supercooled liquid not only flows more easily; but the structure of the liquid is also changed with increased flow. Those very researchers used entropy to describe sheared supercooled liquid dynamics due to a lack of a better answer. We learn in chemistry that Entropy is the measure of molecular order/disorder. That is confusing, but a good example would be that liquid water is more hectic and disorderly due to its flowing structure than ice which has a rigid and solid structure. Therefore, in this scenario the crystal tends to be more ordered than a liquid and thus have lower entropy. Now why is this even relatively important? Trond S. Ingebrigtsen stated, “By considering the arrangement of molecules under shear we could connect the behavior of supercooled liquids under shear to a fundamental concept in physics, namely the entropy; or more specifically, the two-body structural entropy.” On of the most interesting subtopics of research in this subject is structural anisotropy in the liquid. Anisotropy is what is induced after a significant amount of shearing in which the molecules have to keep rearranging and reacting to the movement of the entire molecular ringed structure as a whole. Structural anisotropy shows that the structure measured with respect to the flow direction will turn out to be different and influences the properties of the system as a whole.
In conclusion, the discovery of the connections between shear thinning and anisotropy along with two-body entropy (entropy involving only 2 systems), has opened new doors for scientists to uncover the full mechanism responsible for the shear thinning phenomenon, whoch is the main goal in most research being done by physicists on this topic. A good understanding of the shear thinning process would truly reveal more to the word about molecular motion and their relations with Newton’s law of inertia.