Identify the monomers which forms biodegradable polymers
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Amino caproic acid + glycine
Biodegradable polymers are synthetic polymers that can be broken down by microorganisms in the environment. They are designed to carry functional groups like those of biopolymers, mainly ester and amide links that can be hydrolysed. Two examples are PHBV (an aliphatic polyester) and nylon-2-nylon-6.
Nylon-2-nylon-6 is an alternating polyamide copolymer of glycine (\( \ce{H2N-CH2-COOH} \)) and amino caproic acid (\( \ce{H2N-(CH2)5-COOH} \)):
\( \displaystyle n\,\ce{H2N-CH2-COOH} + n\,\ce{H2N-(CH2)5-COOH} \to \ce{-(NH-CH2-CO-NH-(CH2)5-CO)_{n}-} + 2n\,\ce{H2O} \)
So the monomers that form a biodegradable polymer are amino caproic acid and glycine.
Why the other options are incorrect
Option (1) Ethylene glycol + phthalic acid — Incorrect. These give glyptal, a polyester resin used in paints and lacquers; it is not biodegradable.
Option (2) Caprolactam — Incorrect. It gives nylon 6 (heated with water at 533–543 K), used for tyre cords, fabrics and ropes; it is not biodegradable.
Option (3) Phenol + Formaldehyde — Incorrect. These give bakelite (via novolac), a cross-linked thermosetting polymer; it is not biodegradable.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Nylon 2–Nylon 6
