Zaymiey

🧪 Chemistry  ·  Polymers  ·  NEET & JEE

What is the role of the initiator in free-radical polymerisation?

Answer: Generates free radicals to start the chain reaction.

  • A Generates free radicals to start the chain reaction
  • B Terminates the chain by combining with the growing radical end
  • C Increases molecular weight by adding extra monomer units directly
  • D Lowers the temperature required to sustain the reaction

Correct answer: A. Generates free radicals to start the chain reaction

Explanation: Initiators (e.g., benzoyl peroxide) decompose to generate free radicals that begin the polymerisation chain.

Addition vs Condensation PolymerisationAddition (e.g. polythene)n (CH₂=CH₂)-[-CH₂-CH₂-]ₙ-No atoms lost - monomers just join at the double bondCondensation (e.g. Nylon-6,6)HOOC-R-COOH + H₂N-R'-NH₂-[-CO-R-CO-NH-R'-NH-]ₙ-+ n H₂OA small molecule (water here) is eliminated at EVERY linking step

Addition polymerisation simply links monomers containing a double bond with nothing left over, while condensation polymerisation joins two different monomers through a reaction (often forming an ester or amide bond) that releases a small molecule like water at each step.

Concept context

Large molecules made of repeating monomer units. Covers addition and condensation polymerisation, natural and synthetic polymers (nylon, PVC, Bakelite, natural rubber), and their real-world industrial applications.

Read the full Polymers notes →