100 Nano-Stories: Co-Precursors!
Episode #47: Hydrophilic Aerogel → Hydrophobic Aerogel (Part 2)!
Preface! ✨
It’s your favorite material science & nanotechnology enthusiast! Before we get into today’s topic, let’s discuss some brief concepts real quick!
The article below is a must-read to proceed to the following article! The article is only 7 minutes long! 😁
The essential points in the previous article are as follows:
- Essentially, any molecule that is composed of only oxygen and hydrogen (water) will have polar bonds. Therefore, the molecule will be polar.
- Essentially, any molecule that is composed of only carbon or hydrogen will have non-polar bonds. Therefore, the molecule/organic compound will be non-polar.
- Polar Molecules → Hydrophilic Aerogel.
- Non-polar Molecules → Hydrophobic Aerogel.
- Hydrophilic Aerogels will absorb water and destroy the aerogel.
- Hydrophobic Aerogels will repel water and bounce away from the aerogel.
If you want to know about the first way to turn a hydrophilic aerogel into a hydrophobic aerogel, I will add the article towards the end!
But now that we know what we need to know, let’s move on to how to convert a hydrophilic aerogel to a hydrophobic aerogel!
The Co-Precursor Method! 💡
The Process! 🔑
In simple terms, we try to replace some of the TEOS & TMOS precursors that were already in the hydrophilic aerogels with a different organic compound called organosilane. Once we replace some of the TEOS/TMOS with the organosilane, we can let the gel undergo HTSCD (High-Temperature Supercritical Drying) or LTSCD (Low-Temperature Supercritical Drying). And there we have our hydrophobic aerogel!
My bad, reader! Let’s try to break down the process! 😅
TEOS & TMOS Precursors! 🔑
Let’s define what a precursor is in the first place.
A precursor is a (chemical) compound that participates in a chemical reaction that will produce another (chemical) compound.
A co-precursor is a new substance/chemical compound that is combined with the original/first compound to make the final compound/substance.
Now let’s discuss what TEOS & TMOS precursors are!
TMOS → Tetramethoxysilane/Tetramethyl Orthosilicate.
TEOS → Tetraethoxysilane/Tetraethyl Orthosilicate.
But what does “ortho” mean? 🤔
Ortho in chemistry means that an organic compound/molecule has substituents (additional molecules) at the 1st and 2nd positions on an aromatic compound.
Aromatic compound means that an organic compound/molecule that contains “rings”. These rings have pi bonds, which can result from carbon atoms that have double bonds or triple bonds.
This is how the molecules will appear when undergoing a chemical reaction with an organosilane. The only prerequisite that the organosilane needs to combine with the precursor is that it must have one non-polar group that can bond to the main silicon atom of either the TEOS or TMOS precursor in the gel.
Non-polar molecules are groups that render hydrophobic properties. These properties are what we want to make a hydrophobic aerogel.
But if we want to make sure that we can make a hydrophobic aerogel, what we can do is add a precursor that has a less likely chance to polymerize with the rest of the surface of the aerogel.
Polymerization means smaller molecules will combine to make a large molecule or polymer. You can think of a bee polymerizing another flower: it makes a longer chain of pollen and flowers!
Because there is a lesser chance of polymerization when we add a precursor that can’t polymerize, the aerogel will be able to go from hydrophilic to hydrophobic! And that’s it! Hydrophobicity complete!
Closing Thoughts! 💭
Whew! That was an exhausting article to write, reader! 😵
But it was an essential one to write! And it was fun to explain to all of you!
We are at the final way to turn a hydrophilic aerogel into a hydrophobic aerogel!
Until then, see you tomorrow! ✌🏽
Vocabulary! 📓
Hydrophilic Aerogel → Polar molecules are attached to the surface of the aerogel. Hydrophilic Aerogels will absorb water.
Hydrophobic Aerogel → Non-Polar molecules are attached to the surface of the aerogel. Hydrophobic Aerogels will repel water.
Polar molecules → The electrical charges of the molecule are not evenly distributed. The OH group is a polar molecule commonly found on the surface of hydrophilic aerogels. Polar molecules are hydrophilic.
Non-Polar molecules → The electrical charges of the molecule are evenly distributed. No positive or negative charges are formed in the molecule. All alkanes, alkenes, and alkynes are non-polar molecules because they are composed of carbon and hydrogen.
Polymerization → Smaller molecules will combine to make a large molecule or polymer.
Ortho → In chemistry, “Ortho” means that an organic compound/molecule has substituents (additional molecules) at the 1st and 2nd positions on an aromatic compound.
Aromatic compound → An organic compound/molecule that contains “rings”. These rings have pi bonds, which can result from carbon atoms that have double bonds or triple bonds.
Precursor → A(chemical) compound that participates in a chemical reaction that will produce another (chemical) compound.
Co-precursor → A new substance/chemical compound that is combined with the original/first compound to make the final compound/substance.
TEOS → Tetraethoxysilane/Tetraethyl Orthosilicate.
TMOS → Tetramethoxysilane/Tetramethyl Orthosilicate.
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