The monomer of polytetrafluoroethene is?

• A. Ethane, C2H6
• B. Tetrafluoroethene, C2F4
• C. Vinyl chloride, C2H3Cl
• D. Fluoromethane, CH3F

Answer: (B)

Polymer formation by addition polymerization needs a monomer with a carbon–carbon double bond, a vinyl-type unit that can open up its C=C and link end-to-end. Tetrafluoroethene has that vinyl structure, F2C=CF2, so it can polymerize to form polytetrafluoroethene, giving the repeating unit -(CF2-CF2)- in PTFE. The other options don’t fit: ethane and fluoromethane are saturated and won’t undergo the same vinyl polymerization, and vinyl chloride would polymerize to PVC, not PTFE.