In this video, we're gonna go through how to draw polymers made through condensation polymerization.
Here's the 101 on condensation polymerization,
which is also called step-reaction polymerization.
During the process of making this polymer, small molecules like water, methanol, ammonia or HCl
is formed as a by-product.
Let me try to explain how this works.
Imagine you have two monomers side by side like this. Part of monomer one is
removed and joins together with part of monomer two and they form the by-products.
This happens on both sides of the monomers.
The remaining monomer is then joined together with a linkage.
In this video, I'm gonna focus on two types of condensation polymer,
specifically polyester and polyamide.
These two polymers will condense out water as the by-product.
Let's start with polyester.
It's made from monomer with hydroxyl and carboxyl group. Now this is important.
Hydroxyl group will give out H. Carboxyl group will give out OH.
Just to be clear, hydroxyl group is OH and carboxyl group is C=O, OH.
You might wonder, What's the big deal? It doesn't matter how I take out H and OH, right?
As long as I get H2O? Well, yeah, but the structure of your polymer will be messed up,
and we don't want that, so, you do wanna pay attention that
H comes from hydroxyl group and OH comes from carboxyl group.
Let's start with two monomers.
The one in blue contains the hydroxyl group the one in green contains the carboxyl group.
Let's take out the water. H from hydroxyl. OH from carboxyl.
Taking them out will form two water molecules.
The remaining monomers will join together like this.
This is the structure of the repeating unit in our polyester.
Make sure we have open-ended bonds on both ends.
Then we place in the bracket and n.
That is the shorthand form of our polyester. If you want to show the
repeating units then you can copy down and write out as many repeating units as you need.
That bond that we made linking together the two parts of the monomers
that is called an ester linkage. Now that we've drawn polyester, let's move on to
polyamide. It's made from monomers containing amino group and carboxyl group.
Similar to polyester, you do want to pay attention to where the water
molecules come from. So it's H from the amino group and
OH from the carboxyl group and the remaining monomers will join together to form polyamide.
Let's try forming polyamide. Look at this monomer.
Do you see that it has two different groups within itself?
We can form polyamide with just this one monomer.
Here's what we'll do. We'll line two of them up side-by-side like this.
Then we'll take out H from amino. OH from carboxyl like this.
Let's copy out the remaining monomers, link them up together like this.
That linkage is called amide linkage. We have drawn out the structure of polyamide showing two repeating units.
If we want to show the shorthand version,
all we have to do is copy out the repeating unit like this, place in the brackets and
'n' on the bottom right and we have the shorthand structure of the polyamide.
Just to recap, polyester is made from monomers with hydroxyl and carboxyl group.
They condense out water and join together through ester linkage.
Polyamide on the other hand is made from monomers with amino and carboxyl group.
They join together through amide linkage.
Lastly, don't forget H comes from hydroxyl or amino group and OH comes from carboxyl group.
Hope you find this video helpful.
Do subscribe. Thanks for watching and I'll see you in the next video.
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