And Yet it Moves

I started my blog a bit over four years ago with a post “And Yet it Rotates”. In it I described my first guess at a supramolecular orbital, or a very complex trajectory for the confined closed-loop motion of molecules. While I still definitely believe that molecules mostly move in more-or-less closed-loop orbitals, even when gaseous or liquid, the model that I presented probably isn’t the correct one. Or if it is correct sometimes, it probably doesn’t describe the most common motion. The title of the blog post came from a common misquote of Galileo’s apocryphal quote "Eppur si muove", or “And yet it moves”.

I’ve come a long way since then in developing my theory and having had to prove myself at least a bit wrong several times over. But what hasn’t changed is my initial idea that molecules rotate, at least when they are in a liquid and in a gaseous state. I can allow vibrations for solids.

In the past weeks I’ve been building a crystal model for the solid lignin spheres, where nanotubular lignin crystallites compress into rounded rhombuses. But in today’s post I’m doing something different. I’m showing how these tubules rotate when turned into liquids.

The reason for this apparent conversion from compressed rhombuses to rotating cylinders comes from a very concrete chemical truth. In general solids react much more poorly than liquids. So, what we do in my company is add reagents to the solid powder of lignin spheres and convert the powder into a liquid. Some people (such as peer revewers) could suggest that the liquid isn’t turning the powder into a liquid, but rather it is merely converting the dry powder into a liquid suspension. The problem is that the volume ratio of the powder of lignin spheres to the reagent is so large that it is impossible for such a tiny amount of liquid to suspend these sphere. Rather, the only possible explanation is that the spheres, made of hollow lignin nanotubules, absorb the liquid within them, turning the theoretically liquid-solid hybrid into a fully liquid state.

And why do I say this converts the nanotubes in the mixture into a liquid? Well, if the liquid used for infusing is not the correct kind, the liquid-solid mixture is indeed a colloidal suspension, that behaves exactly like one would expect of such a colloid, including being highly thixotropic, or shear-thinning. But when the liquid is compatible, the colloids are no longer insoluble, but turn into a partially liquid state, or more specifically a liquid crystal state. Even more specifically, in a rod-like, or calamitic state. When these rods form a liquid crystal, this is called a nematic phase.

So, what properties does this liquid lignosphere solution have? Well, while the thixotropy in colloids means that unless they experience considerable shear force, they remain solid. But upon shear the solid converts into a very runny liquid. This is because the colloids are individual solid  objects that require the force to make the whole particle move. But when converted into nematic liquid crystal, the whole sphere doesn’t need to move when experiencing outside forces. Rather, the individual cylinders can rotate. And while the rotation of the outermost cylinders will transmit the force to its neighbors, a single cylinder is only connected to four neighboring cylinders at maximum, meaning that, meaning a more even transfer of angular momentum. And this means that one does not require a huge initial shear force to get the spherical particle moving, because the particle is no longer a single solid object, but a collection of liquid rods.

To illustrate this coupled rotation, I decided to learn to animate this, using geometry nodes in Blender. Aided by ChatGPT I was able to make this still relatively crude animation:

https://video.wixstatic.com/video/ed0781_3f74b09042a34a4abe9a1dc7ddd1fa46/1080p/mp4/file.mp4

Because I feared that the rotation of featureless cylinders wouldn’t necessarily be obvious, I introduced a small cylindrical protrusion (or a bump) to the edge of the hollow tube, just to make the rotation pop out more. Perhaps I will replace this with something as visible, but less misleading, such as an arrow mark, for future illustrations.

While there isn’t exactly anything scientifically new for me in this post, I think it illustrates what takes place in the particles much better than my spinning 3D models. And now that I know how to do these illustrations better, I might start doing all of my animations with Blender, instead of using PowerPoint.

I don’t know about you, but somehow this simple animation brings up unexpected joy in me.