JEE Main 2022 · 28 June · morning · Single correct · +4 / −1
Which one of the following is NOT a copolymer?
- (a) Buna-S
- (b) Neoprene
- (c) PHBV
- (d) Butadiene-styrene
Answer and solution
Answer (b) Neoprene
Solution
Chemistry ma’am · 3 steps
Find each polymer's monomers: a copolymer needs two different ones, and only neoprene has just one.
- What a copolymer is. A copolymer is built from two or more different monomers. A homopolymer repeats a single monomer again and again.
Polymer Monomer(s) Type Buna-S 1,3-butadiene and styrene copolymer Neoprene chloroprene (2-chloro-1,3-butadiene) only homopolymer PHBV 3-hydroxybutanoic acid and 3-hydroxypentanoic acid copolymer Butadiene-styrene 1,3-butadiene and styrene (this is Buna-S) copolymer - Neoprene. Neoprene forms by addition polymerisation of chloroprene alone: n CH₂=C(Cl)-CH=CH₂ → -[CH₂-C(Cl)=CH-CH₂]ₙ⁻. Every repeating unit is the same.
- So. Neoprene is the only homopolymer in the list, so the answer is (b).
The idea to keep. To sort copolymers from homopolymers, write down the monomers. Count the different monomers, not how many molecules join up.
Answer from the NTA final answer key. Solution by PrepWiser.