Condensation polymers find widespread use in material science due to their distinctive mechanical properties, which are heavily influenced by the nature of the intermolecular forces between their chains.
Which of the following repeating units represents a condensation polymer that can form hydrogen bonds between adjacent polymer chains?
−[O−CH2CH2−O−C(=O)−C6H4−C(=O)]n−-\left[\text{O}-\text{CH}_2\text{CH}_2-\text{O}-\text{C}(=\text{O})-\text{C}_6 \text{H}_4-\text{C}(=\text{O})\right]_n-−[O−CH2CH2−O−C(=O)−C6H4−C(=O)]n−
−[NH−C6H4−NH−C(=O)−C6H4−C(=O)]n−-\left[\text{NH}-\text{C}_6 \text{H}_4-\text{NH}-\text{C}(=\text{O})-\text{C}_6 \text{H}_4-\text{C}(=\text{O})\right]_n-−[NH−C6H4−NH−C(=O)−C6H4−C(=O)]n−
−[O−CH(CH3)−C(=O)]n−-\left[\text{O}-\text{CH}(\text{CH}_3)-\text{C}(=\text{O})\right]_n-−[O−CH(CH3)−C(=O)]n−
−[O−CH2−C(CH3)2−CH2−O−C(=O)−C(=O)]n−-\left[\text{O}-\text{CH}_2-\text{C}(\text{CH}_3)_2-\text{CH}_2-\text{O}-\text{C}(=\text{O})-\text{C}(=\text{O})\right]_n-−[O−CH2−C(CH3)2−CH2−O−C(=O)−C(=O)]n−
