Introduction to Polymers - Online Tutor, Practice Problems & Exam Prep

Polymers are large molecules formed from repeating units called monomers, with molecular weights ranging from 10⁴ to 10⁶ atomic mass units. They can be classified into chain growth and step growth polymers. Chain growth polymers are formed by adding monomers to the ends of a growing chain, while step growth polymers form through the combination of different monomer fragments. Understanding these classifications is essential for grasping polymer chemistry and its applications in everyday materials like plastics.

Introduction to Polymers Concept 1

Hey, everyone. Let's take a look at the introduction to polymers. Now, polymers themselves are large molecules made from small repeating units called monomers. And we're going to say here that polymers have very high molecular weights ranging from 104 atomic mass units up to 106 atomic mass units. Now, if we take a look, envision that monomers are represented by these spheres.

And we're going to say through the process of polymerization, we're able to connect these monomers together, and in doing so, create a string of monomers called a polymer. Now if we take a look at an organic molecule, we have ethene here, which is a simple alkene. Through the use of a catalyst, we're able to string them together, so numerous ethenes together, many ethenes together. Remember, the word many, the prefix here we could say is poly. So we have a polyethylene, which is many ethenes together.

And we're going to say here what they have in common is this ethylene group. It's what's being repeated over and over again, so each one represents a repeating unit. Now here, plastics, they're just polymers that can be molded when hot and retain their shape when cooled. So example, our polyethylene. Now here you might see this water bottle in the top right corner.

It's a plastic water bottle, so it also is a polymer. So we can see that polymers can be used for everyday items such as this plastic water bottle. So just remember, we have monomers. Monomers strung together help to create polymers.

Introduction to Polymers Example 1

Hey everyone. So in this example, it says, name and draw the repeating unit of a polymer that results from the polymerization of acrylamide. Here we have acrylamide, which is an amide group, and we have this alkene portion. Remember, in our previous video, we talked about ethene, which was these two carbons double-bonded to each other, which is essentially similar to this portion right here. We can say that this pi bond here, that pi bond is what we can use to string these acrylamides together.

So we'd have CH₂ and then CH, which is this CH, which is still connected to this carbonyl and this amino group. And then the next acrylamide uses its pi bond to connect to it with its carbonyl and amino group. And then the next acrylamide… So we have many acrylamides together. The word for many is poly.

So this could be our polyacrylamide. And then we could say that this represents our repeating unit. That's what we see being done over and over again. So that's our repeating unit right there, right?

This is what we can say in terms of this example question, the name of our polymer chain, and the identity of our repeating unit.

Introduction to Polymers Concept 2

Everyone, in this video, let's talk about the types of polymers. We're going to say, depending on the mode of assembly of monomers, polymers can be classified as either chain growth polymers or step growth polymers. Now, with a chain growth polymer, these are monomers being added to the ends of the growing polymer chain. So, if we take a look here, we have these monomers in these blue spheres, so they're all the same type of monomer.

What happens is that 2 of the monomers decide to link up together to make a dimer. And what starts happening is we start adding to the ends of each of these monomers, lengthening our chain. So here we're going to say the chain grows at the ends. And now, this monomer can link up from this end, and this one here, making the chain even longer. So, here we have a longer polymer chain.

Now, step growth polymers are different. These monomers form fragments, which combine in steps to form polymers. So here, notice that we have different shades of these monomers, indicating that they may not be the same. What happens here is that they can connect together to make different combinations. Here we have 2 of them together, that's a dimer, or we can have them 3 together, that's a trimer, or even 4 of them, which is a tetramer or tetramer.

Now here, they can then link up with each other, and we're going to say the polymers form in steps here. What we start having here is our polymer that's been created or a chain here. And we can see in this example, they're alternating. We'll talk about the different combinations and the patterns that can arise later on. But in this particular example, we're showing that with our step growth polymers, the different monomers are forming larger or smaller fragments, such as dimers or trimers.

And then those pieces are what connect together to make our official polymer chain. So just remember, when we're talking about different types of polymers, the big picture is we have our chain growth polymers and then our step growth polymers. Right. So that's how we can classify them on a broad category level.

Introduction to Polymers Example 2

In this example question, it asks, which one of the following statements is correct about polymers? Chain growth polymers can be molded by heat, while step growth polymers can be molded by high pressure. Remember, it doesn't matter if it's a chain growth polymer or a step growth polymer, they both can be affected and molded by heat. Next, the polymer chain grows by a combination of smaller fragments in step growth polymers. This is true.

When it comes to step growth polymers, our monomers can combine in different combinations such as dimers or trimers, which then connect together to make our polymer. In chain growth polymerization, monomers are consumed first to form dimers and trimers. So remember, this isn't chain growth, this is step growth. In step growth polymerization, the polymer grows by continuously adding monomers on both ends. No.

This is not chain growth polymerization; this is step growth polymerization. So out of our four choices, the only one that is correct is option b.