Problem 79 - Chemistry An Atoms First Approach

Question

Polystyrene can be made more rigid by copolymerizing styrene with divinylbenzene: How does the divinylbenzene make the copolymer more rigid?

Step-by-Step Solution

Answer

Divinylbenzene makes the polystyrene copolymer more rigid by creating cross-links between copolymer chains during the copolymerization process. This results in a three-dimensional network structure, which enhances the rigidity of the material compared to linear polystyrene.

Step 1: Understand the molecular structure of styrene and divinylbenzene.

Styrene is a monomer with a benzene ring attached to an ethylene chain (-CH=CH2). Divinylbenzene also contains a benzene ring but has two ethylene chains attached to it. The molecular structure of styrene is: C6H5-CH=CH2 whereas the molecular structure of divinylbenzene is: C6H4-CH=CH2-CH=CH2

Step 2: Understand the polymerization of styrene

During the polymerization of styrene, the ethylene bonds of the styrene molecule break and create new covalent bonds with other styrene molecules. This forms a linear chain of polystyrene. The linear chain provides polystyrene with flexibility and elasticity but lacks rigidity.

Step 3: Copolymerization of styrene and divinylbenzene

In the copolymerization process, styrene and divinylbenzene monomers combine, and the ethylene bonds of both monomers break to form new covalent bonds with each other. Since divinylbenzene has two ethylene chains, it can form cross-links with other styrene/divinylbenzene chains. These cross-linked chains form a three-dimensional network structure, which makes the copolymer more rigid.

Step 4: Conclude the effect of divinylbenzene on rigidity

The divinylbenzene, with its two ethylene chains, creates cross-links between the copolymer chains during the copolymerization process. These cross-links result in a three-dimensional network structure that increases the rigidity of the polystyrene copolymer.