1. Liquid Crystals: source of life and of technology
October 11, 2017

2. Liquid crystals
Liquid crystals are the materials that make up the screens of your computer, your phones, your watches.
Even before their technological applications they are the molecules that are responsible for life.

3. What makes them so desirable for life and technological applications
They can be made of molecules that look like pencils or like coins.
You can do the following experiment:
Join together so that all of you have at least pencils
Join together so that you have at least 8 – 10 coins of the same denomination.
Designate one person to hold the pencils. Open your hand and release them close to the floor, not pushing them
Do the same thing with the coins.
Now, take the pencils and the coins and release them at a distance that is further from the floor and almost push them

4. What makes them so desirable for life and technological applications
These shapes tend to align such that the long axis of the pencils are more or less in the same directions and the coins have their surface aligned in the same direction.
This property is what is called the self aligment, because given certain temperatures and/or concentrations they will align as described above.
Self-alignment will depend on the temperature (which we did by tossing the coins from a larger distance from the floor and “pushing” them as they were tossed) and /or the concentration of the liquid where they are dispersed in.

5. Real molecules C8H17 CN Coin shaped Pencil shaped
Peter J. Collings and Michael Hird, Introduction to Liquid Crystals, Taylor and Francis, 1997

6. The arrangement can tell us of at least two phases
The nematic or the most disordered of the ordered phases
And the isotropic or the disordered phase
Peter J. Collings and Michael Hird, Introduction to Liquid Crystals, Taylor and Francis, 1997 N

7. If you are more careful at putting together the pencils and coins, we get more ordered phases
Sm-A
Peter J. Collings and Michael Hird, Introduction to Liquid Crystals, Taylor and Francis, 1997

8. How can self-alignment help in technological applications
One can choose a liquid crystal such that at temperatures oscillating between RT (25C or 75F) to the boiling point of water (100C or 212F) they are aligned, but not in the same direction.
We can use external fields such as an electrical or magnetic field to manage the self alignment such that if the molecules were originally pointing every which way right when the field is applied they point in a certain direction.
These can form numbers (watches, displays) or images (TV’s, computers, telephones)

9. Real molecules C8H17 CN Coin shaped Pencil shaped
The areas in circles are electron-rich. By choosing the appropriate molecules and combining in the right geometry them with other molecules or solid materials one can fabricate a photovoltaic.
Peter J. Collings and Michael Hird, Introduction to Liquid Crystals, Taylor and Francis, 1997

10. The molecules of life are slightly different.
They are designed (by nature) to have a hydrophilic head (the nitrogen group at the end) and hydrophobic tail (the carbon chains)
They change phases by varying the concentration of liquid in which they are mixed into.
These molecules are known as lyotropic molecules
A well known biological molecule which is a liquid crystal is DNA
Peter J. Collings and Michael Hird, Introduction to Liquid Crystals, Taylor and Francis, 1997

11. They have different phases but the one favorable for life is the lamellar phase
With a change in the concentration one can get the hexagonal phase, which in many ways is not a continuously closed surface, except perpendicular to the edges of the hexagon
Peter J. Collings and Michael Hird, Introduction to Liquid Crystals, Taylor and Francis, 1997
Several different illnesses can result if a phase change happens (or there is a change in the concentration of water)

12. In order for cells to perform their functions….
They must have form and structure
There must be mechanisms that allow materials to enter and exit the cells.
Liquids do not have form or structure, but do provide a medium for the efficient transportation of materials
Solids have form and structure but do not allow for the efficient movement of materials.
We need a phase intermediate between solid and liquid that shares properties with both these phases. This is the liquid crystal phase

13. In other words… Do we want to be made out of steel (like Superman)?
Do we want to be blobs of water or any other liquids (like the Blob)?