When styrene (vinylbenzene) is commercially polymerized, about 1–...

Question

When styrene (vinylbenzene) is commercially polymerized, about 1–3% of 1,4-divinylbenzene is often added to the styrene. The incorporation of some divinylbenzene gives a polymer with more strength and better resistance to organic solvents. Explain how a very small amount of divinylbenzene has a marked effect on the properties of the polymer.

Accepted Answer

Welcome back everyone. During commercial polymer Ization of polyethylene, 2% peroxide is sometimes added to the mixture. The addition of some peroxide gives a stronger product with higher flexibility. Explain how this small quantity of peroxide can have such a large effect on the properties of polyethylene. So we're going to begin by drawing out our polymer will represent it by the following chain with these dashed links at the end to represent our constant repetition of these chains. And we're going to place a coefficient of two here to represent that we have two moles of this. And more specifically, this coefficient of two is referring to the number of monomers combined to form each repeating unit in our polymer chain. So, as the prompt states, we have peroxide as our reactant will represent it as R O R. And we want to recall that peroxide is a, let's say peroxide is a strong oxidizing agent. And due to this being a strong oxidizing agent, this peroxide is going to initiate our polymer Ization of polyethylene by taking one of the hydrogen atoms that are implied here and abstracting it. And so the bond that hydrogen has with the carbon, one of the electrons is going to be removed to bond with the peroxide and then the remaining electron is going to fall onto the structure. Sorry, let's draw that clear is going to draw fall onto the structure as a radical electron. And so what we would produce is two moles of our following polymer where we have now a radical at this location. So a radical electron represented by this dot here. So technically this part of our process is a initiation. And then at this point we have our polymer ization occurring. Where are radical polymer structure is generated here. I'm sorry, this says polymer ization. And so we would use another molecule of peroxide in our polymer ization where we would form the falling polymer, which is now going to be a cross linked form of our polyethylene. So notice that I've drawn this linked bond here. So now we have this covalin bond that is linking these two polymers. So let's note down that this is cross linked polymers. And as you can see, we have a product that is a much more three dimensional three dimensional network of these two polymer chains here. And because of this cross linked product, we can now say that we have higher rigidity of the structure, meaning we have tight constraints between the bonds that make up this product. We also will have a greater value or magnitude of hardness for this product. And we will also have a higher melting point for this cross linked product. And this is why a lot of the plastics that we use daily are all consisting of cross linked structures at the molecular level. Now, if we were not able to use peroxide for our polymer ization, these individual chains of our polyethylene are going to slide past one another. And so that is why through this Covalin bond linking our polymer structures here, where we have a greater value of rigidity, as we stated, preventing these polymer chains from sliding. And so we can also detail that cross linked polyethylene has low tension, high flexibility and a softer and tougher structure compared to just ordinary polyethylene. So, for our final answer, we can confirm that our product cross linked polyethylene is produced from polymer ization initiated by peroxide, which results in a strong and flexible product, which is again our cross linked polyethylene. So this entire statement is going to be our final answer, which corresponds to choice a in the multiple choice. I hope that everything I reviewed was clear. If you have any questions, please leave them down below and I'll see everyone in the next practice video.

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