Which polymer family ranges from rubbery to brittle and is formed by the reaction of diisocyanate with a hydroxylic compound?

• A. Polyurethane
• B. Polyamide
• C. Polyethylene
• D. Polystyrene

Answer: (A)

Polyurethanes form when a diisocyanate reacts with a hydroxy-containing compound to create urethane bonds. By choosing different diisocyanates and polyols, the material develops soft, rubbery segments or hard, stiff segments, and the proportion between these segments can be tuned. That flexibility is what lets the same polymer family span from elastic, rubbery forms to rigid, brittle plastics. The urethane linkage is the defining feature that links the monomers in this way, giving properties that can be tailored for foams, elastomers, coatings, and more. This is different from polyamides, which are built from diamines and diacids forming amide bonds, and from polyethylene and polystyrene, which are simple hydrocarbon polymers made by straightforward addition polymerization without urethane linkages.