Copolymers - Online Tutor, Practice Problems & Exam Prep

Copolymers consist of two or more different monomers, unlike homopolymers, which are made from a single type. They can be categorized into four types: alternating copolymers, where monomers alternate in a regular pattern; random copolymers, with no discernible sequence; block copolymers, featuring large blocks of alternating monomers; and graft copolymers, which have branches of one homopolymer grafted onto another. Understanding these structures is essential for applications in materials science and polymer chemistry.

Copolymers Concept 1

In this video, let's take a look at copolymers. Now, here we're going to say we have homopolymers and copolymers. First of all, homopolymers are made up of a single type of monomers. And when we say this, they're all going to be the same shape, same size, and color, but copolymers, we're going to say they're made up of 2 or more different monomers together. Now they're subdivided into different types based on the arrangements of their monomers in the polymer chain.

Now here, let's take a look at the different types of copolymers. In the first one, we can see that it goes a b a b a b in this discernible pattern. And it's alternating between a and b, and that's why it's an alternating copolymer. Now here, 2 monomers alternate in regular sequence. The next one, we still have a b e s, but here we're going to say 2 or more monomers arranged in random sequence.

There's no discernible pattern that we can see here, so this is random. Next, we're going to say large blocks of monomers alternate with one another. So here, b's and then a's together and then b's again b's together again. They're alternating in blocks and that's why we call this a block copolymer. Then finally here, we have our chain of a and branching off it are b's.

So here, we're going to say we have homopolymer branches grafted into another homopolymer chain. So this is a homopolymer chain because it's all a's and these are the branching groups which are also homopolymers. Grafting meaning they're branching off, so we call this a graft copolymer. So just remember, these are the different types of arrangements that can occur for different types of copolymers.

Copolymers Example 1

In this example, it says to provide a structure of the alternating copolymer formed from the following set of monomers. Alright. So here we have our pi bond, and here we have a pi bond. We're connecting them together. So we're going to say here we start out with our CH₂, which is this CH₂.

It's connected to some rest of this polymer, so we're not going to worry about that. We're just trying to show the alternating copolymer, so the repeating unit. Alright. So now it's connected to this CH, which is connected to the chlorine, which is this. Our pi bond can act as a bridge to this other CH₂ right here.

We'll put this one here in blue. It is connected to this carbon here, which is connected to two methyls. Then we have this bond here. So then we say that there's an x number of them. We don't know, so we put the subscript n here to show that this is just one alternating copolymer in a sequence, a long polymer chain.

Alright. So this is how we display our alternating copolymer based on the two reactants given, they being vinyl chloride and isobutylene.

Draw a short segment of SBS (styrene-butadiene-styrene) block copolymer.

Here, we're told to draw a short segment of SBS, which is styrene, butadiene, styrene, as a block copolymer. Alright. So we have styrene, butadiene, butadiene, and then styrene again. So we need to draw another styrene. So we're going to draw our CH2 double-bonded to CH connected to a benzene ring. Now the way you have to think about it is these things are linking up, connecting. This here can connect to here, but that causes a cascading effect where this comes here, which causes this to come here and attach. And then this here out to, if we want another compound, another butadiene. But here, they only want us to show these three together. Alright. So, what does that look like? Well, we have our CH2 here. And again, it's connected to stuff outside, but we're not worried about it. It's connected to CH and then our benzene. That is then connected to this CH2 which is then connected to a CH, this CH, which is double-bonded to this CH because remember the pi bonds moved which is then connected to the CH2. Here we're showing it as a SIS orientation because that's most ideal to connect these. And then we're gonna have this CH2 connecting to this CH2. And that's connected to CH, which is then connected to this benzene as well. And then we can say that it's connected to something else. Now here we can say that there's an n number of these. There's an n number of these. And again, an n number of these. But that's how we're able to connect them together in the form of this block copolymer. Alright? So just realize here I have to give us the sequence to tell us the order in which they're connecting to each other.

Identify (draw) monomers used to form following copolymer.

In this practice question, it says, identify and draw the monomers used to form the following copolymer. Right? So the way you need to look at it is we have our electron withdrawing group here, yes. And it's connected to this CH, and it has to be connected to this CH2. Why is that a CH2? Because we could say that this bond here, if you want to think about it that way, was a pi bond. So we had a CH2 here connected to CH, connected to our electron withdrawing group. So that's one monomer. And then the rest of it would be the other one. So here's the rest of our structure. So let's think about it here, CH2. It's a CH2 because it's double-bonded to this CH, and that CH is connected to this oxygen, which is connected to this carbonyl, which is connected to this methyl right here. Right? So this would represent our two monomers that we connected to create this copolymer at the end.