100 Nano-Stories: How Did You Fix My Aerogel?

Episode #15: Explaining Aerogel Hydrophobicity!

Carlos Manuel Jarquín Sánchez
5 min readJan 16, 2021

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How does the water not pass through the aerogel? Photo by ReserachGate.net

Preface

All right, I’m back from drinking my glass of water! Now, let’s move on to the different types of chemicals and explain the power of hydrophobicity!

Carlos, did you forget that there are new readers to your series?

Oh, shoot! I forgot about that! Thanks for reminding me, reader! Here’s the previous article that will discuss what types of chemicals we will be discussing for this article!

Thanks for helping me… er, I mean the new readers understand what you will talk about! 😁

Silyation Hydrophobes Explained!

What is Silyation, Carlos? I never heard of this term.

Silyation is the process where we replace hydrogen in the Si-OH groups and replace it with a hydrophobe, mostly known as CH3-Si or SiR3. We do this to make the surface of a silica gel go from polar to non-polar. This means that the positive and negative charges of a molecule are evenly spread out, so no charges are formed on the molecule.

But why does that matter, Carlos?

H2O (Water) and the Si-OH molecules that make up the surface of the silica gel are both polar, which allows them to attract to tach other and absorb water, which destroys the aerogel completely.

Ohhh! Now I understand why we need to make them hydrophobic!

Yup! But if you remember in the last article, R3 is only one description of a chemical. Confused? This photo demonstrates the chemical reaction of silyation.

Hydrophilic Aerogel → Hydrophobic Aerogel. The chemical structure is rearranged! Photo by Carlos Jarquin.

Yup! I see the R3 in the molecule! But why is the R3 so important?

“R” stands for an abbreviation of another atom attached to a larger molecule/ion. Most of the time, it is used to describe a Carbon and/or Hydrogen Atom. For this article, “R3” is “CH3” (CH3-Si Bond).

Thank you, Carlos! I thought that “R” was also used for The Universal Gas Constant, or the one-letter abbreviation for the amino acid arginine!

How about we stick to aerogels, reader? If you want, you can make an article about that! 💡

CH3 (R)is toluene, which is a hydrocarbon that consists of a methyl group. Or, you can say that it is a nonpolar aprotic solvent.

WTF are these terms? Photo by Meming World.

Yeah, you’re right, I need to explain all of this, or otherwise, you’ll look like Nick here for the rest of the series. I already defined what a Toulene is, but let’s try and simplify this!

But why should I care?

Well, if we don't finish off explaining the chemistry of silica aerogels, how are we going to talk about the aerogel jacket and swimsuits that you could be wearing in the future?

Never mind. Carry on, Carlos! 😁

A Hydrocarbon is a molecule that only contains hydrogen & carbon atoms!

Wait, Carlos! CH3 is only 1 carbon atom & 3 hydrogen atoms! Is that a hydrocarbon?

¡Exactamente!

Now, what is a methyl group? To define this, we need to bring out a chemical that we commonly use in aerogel production: Methane! Look at the molecular structure of methane in this photo! What do you notice?

Well, there are these solid lines, 1 carbon atom, and 4 hydrogen atoms.

Well, a methyl group is the same photo, but you remove one hydrogen atom: CH3.

Wait, what!? Thats it? No mathematical formula, or fancy tricks?

Would you like to, reader?

How about we continue breaking down what a Toulene is, Carlos? 😅

Nonpolar means that the positively & negatively charged forces in an atom/molecule are evenly spread out, so no positive or negative charge is formed on the molecule. The electrons are shared equally.

So, is that communism for atoms, Carlos?

Hahaha, reader. But let’s stay serious.

Finally, we have an aprotic solvent. But let’s pay attention to these two words. Let’s divide this term into two words to be defined.

A solvent is a liquid/solid substance that is dissolved to form a solution (our aerogel!). But what about aprotic?

Aprotic means that it has no O-H bonds or N-H bonds. More specifically, this means that no Hydrogen Atoms are bonded with Oxygen or Nitrogen Atoms in a molecule.

Woah! That makes so much sense! But can you now rephrase the original definition?

A toluene is a molecule containing only carbon and hydrogen atoms that consist of 1 carbon atom and 3 hydrogen atoms. This molecule is nonpolar and the hydrogen atoms do not bond with an oxygen or nitrogen atom.

Thank you, Carlos! But why should I remember this?

Well, we are only about 5 articles away from talking about aerogel jackets & swimsuits!

Jackets! Photo by Stellar Equipment.

Vocabulary →📓

Solute → A substance (either solid or liquid or gas) that is dissolved in a solvent.

Solvent → The liquid in which a solute is dissolved to form a solution.

Non-Polar → The positively & negatively charged forces in the water molecule are evenly spread out, so no positive or negative charge is formed on the molecule.

Silyation → The process where we replace hydrogen in the Si-OH groups with a hydrophobe; to make the surface of a silica gel go from polar to non-polar.

“R” → An abbreviation of another atom attached to a larger molecule/ion; specifically Carbon and/or Hydrogen Atoms.

Hydrocarbon → A molecule that only contains Hydrogen & Carbon Atoms.

Methyl Group → CH3. CH3 is a molecule similar to methane (CH4), but you remove one hydrogen atom.

Solvent → A liquid/solid substance that is dissolved to form a solution.

Aprotic → A molecule lacks O-H bonds or N-H bonds. No Hydrogen Atoms are bonded with Oxygen or Nitrogen Atoms.

Toluene → A molecule containing only carbon and hydrogen atoms that consist of 1 carbon atom and 3 hydrogen atoms. This molecule is nonpolar and the hydrogen atoms do not bond with an oxygen or nitrogen atom.

O → Oxygen

H → Hydrogen

Si → Silicon

R3 → A Hydroxyl Group (OH)

Resources + Bonus Content →💻

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© 2021 by Carlos Manuel Jarquin Sanchez. All Rights Reserved.

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