Chapter 26, Problem 26.52P

Interpretation Introduction

Interpretation:

Poly(ethylene terephthalate) is a linear polyester that can be synthesized from the condensation polymerization between terephthalic acid and ethylene glycol. The alcohol we would react with terephthalic acid to produce a branched polyester is to be found. A portion of the resulting polymer that shows a main chain and one branching point is to be drawn.

Concept introduction:

Step-growth polymerizations are referred to as condensation polymerization, because a small molecule (in this case, water) is formed as a product. Step-growth polymerization occurs when molecules throughout a mixture join with any other molecule that has an appropriate functional group available to react, whether it is a monomer unit or another polymer molecule. Many nucleophilic addition–elimination reactions can be used to make step-growth polymers. The condensation polymerization between terephthalic acid and ethylene glycol is also called as the Fischer esterification:

The linear alcohol, ethylene glycol, forms a linear polymer. Therefore, in order to form a branched polymer, a branched alcohol is required. Branching can occur during polymerization when a monomer has multiple reactive sites. Such a branched alcohol is $\text{ethane-1, 1, 2-triol}$ which can be used here to produce branched polyester.