Question

Polyesters containing double bonds are often crosslinked by reacting the polymer with styrene. a. Draw the structure of the copolymer of \(\mathrm{HO}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{OH} \quad\) and \(\quad \mathrm{HO}_{2} \mathrm{C}-\mathrm{CH}=\mathrm{CH}-\mathrm{CO}_{2} \mathrm{H}\) b. Draw the structure of the crosslinked polymer (after the polyester has been reacted with styrene).

Short answer

The copolymer structure of the given monomers is \(\mathrm{HO}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{O}-\mathrm{CO}-\mathrm{CH}=\mathrm{CH}-\mathrm{CO}_{2} \mathrm{H}\), where the hydroxyl group of one monomer reacts with the carboxylic acid group of the other forming an ester linkage. The crosslinked polymer structure after reacting with styrene can be represented as \(\mathrm{[HO}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{O}-\mathrm{CO}-\mathrm{CH}-\mathrm{CH}-\mathrm{CO}_{2} \mathrm{H][styrene]_{n}\), where styrene molecules connect to the copolymer through the reactive double bonds forming a crosslinked network.

Step-by-step solution

Identify the reactive groups in the monomers

The reactive groups in the given monomers are the hydroxyl groups (\(\mathrm{OH}\)) in \(\mathrm{HO}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{OH}\) and the double bond (\(\mathrm{C}=\mathrm{C}\)) and carboxylic acid group (\(\mathrm{CO}_{2} \mathrm{H}\)) in \(\mathrm{HO}_{2} \mathrm{C}-\mathrm{CH}=\mathrm{CH}-\mathrm{CO}_{2} \mathrm{H}\).

Combine the monomers through a condensation reaction

In a condensation polymerization reaction, the hydroxyl group of one monomer reacts with the carboxylic acid group of the other monomer to form an ester (\(\mathrm{COO}\)) linkage and a molecule of water. The double bond in the second monomer remains unreacted. The resulting structure is shown below: \(\mathrm{HO}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{O}-\mathrm{CO}-\mathrm{CH}=\mathrm{CH}-\mathrm{CO}_{2} \mathrm{H}\) B. Drawing the crosslinked polymer structure

Identify the reaction of styrene with the copolymer

Styrene has a double bond between two carbon atoms, which makes it reactive and capable of reacting with the double bond in the copolymer created in part A.

Draw the crosslinked polymer

The reactive double bond in the copolymer can react with styrene to form a crosslinked structure. The crosslinked structure can be represented as: \(\mathrm{[HO}-\mathrm{CH}_{2} \mathrm{CH}_{2}-\mathrm{O}-\mathrm{CO}-\mathrm{CH}-\mathrm{CH}-\mathrm{CO}_{2} \mathrm{H][styrene]_{n}\) In this structure, the styrene molecules are connected to the copolymer through the reactive double bonds, forming a crosslinked network.