Which of the following polymers would be stronger or more rigid? Explain your choices. a. The copolymer of ethylene glycol and terephthalic acid or the copolymer of \(1,2\) -diaminoethane and terephthalic acid $\left(1,2 \text { -diaminoethane }=\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)$ b. The polymer of \(\mathrm{HO}-\left(\mathrm{CH}_{2}\right)_{6}-\mathrm{CO}_{2} \mathrm{H}\) or that of c. Polyacetylene or polyethylene (The monomer in polyacetylene is ethyne.)

We have to compare the copolymer of ethylene glycol and terephthalic acid with the copolymer of 1,2-diaminoethane and terephthalic acid. The copolymer of ethylene glycol and terephthalic acid is essentially poly(ethylene terephthalate), or PET. PET is a polyester with ester linkages between the terephthalate and ethylene glycol units. The structure is relatively linear, with no strong interchain interactions. The copolymer of 1,2-diaminoethane and terephthalic acid is a polyamide, also known as a nylon. Nylons have amide linkages between the diaminoethane and terephthalic acid units. The amide groups form hydrogen bonds with each other, leading to strong interchain interactions. So, the copolymer of 1,2-diaminoethane and terephthalic acid will be stronger and more rigid than the copolymer of ethylene glycol and terephthalic acid.

We need to compare the polymer of HO-(CH2)6-CO2H, which is a polyester, with that of an unknown polymer. However, there is no information about the polymers in option b. The comparison cannot be done with the limited information provided.

We have to compare polyacetylene with polyethylene. Polyethylene is a simple polymer made up of CH2 units and has a linear structure. This polymer does not have any strong interchain interactions. Polyacetylene has a conjugated structure with alternating single and double bonds, which creates a π-electron system that extends across the polymer chain. This conjugated system allows for strong interchain interactions through van der Waals forces. Thus, polyacetylene is expected to be stronger and more rigid compared to polyethylene. In conclusion, the copolymer of 1,2-diaminoethane and terephthalic acid and polyacetylene are expected to be stronger and more rigid compared to their counterparts, the copolymer of ethylene glycol and terephthalic acid and polyethylene respectively.