Which one of the following polymers is prepared by addition polymerisation ?

The correct answer is Teflon.

To understand why, we need to recall the two main mechanisms by which polymers are formed:

1. Addition (chain‑growth) polymerisation
– Starts from a monomer that contains at least one carbon–carbon double bond (or another unsaturated group).
– The double bond opens and the monomer adds to a growing chain without the loss of any small molecules.
– Example reaction: $n\; \backslash ,\; \backslash text\{CF\}\_2\backslash !=\backslash !\backslash text\{CF\}\_2\; \backslash ;\backslash xrightarrow\{\backslash text\{radical\; initiator\}\}\backslash ;\; \backslash text\{(–CF\}\_2\backslash !-\backslash !\backslash text\{CF\}\_2\backslash text\{)\}\_n\backslash end\{math>$

2. Condensation (step‑growth) polymerisation
– Involves two different monomers, each bearing at least two functional groups (e.g., –OH, –COOH, –NH₂).
– Each step joins two monomer units and eliminates a small molecule such as water, methanol, or HCl.
– The molecular weight builds up gradually as oligomers link together.

Now examine each polymer listed in the question:

Novolac – A phenol‑formaldehyde resin produced by the condensation of phenol with formaldehyde, releasing water. This is a classic condensation polymer.

Dacron – The trade name for polyethylene terephthalate (PET). PET is formed by the condensation of terephthalic acid (or its dimethyl ester) with ethylene glycol, eliminating water or methanol.

Nylon‑66 – Synthesised from hexamethylenediamine and adipic acid. Each amide link is created by a condensation reaction that releases water.

Teflon – The common name for polytetrafluoroethylene (PTFE). Its monomer is tetrafluoroethylene, \(\text{CF}_2\!=\!\text{CF}_2\), which contains a carbon–carbon double bond. Polymerisation proceeds via a free‑radical addition mechanism, adding monomer units one after another without any by‑product.

Because Teflon is formed by the addition of an unsaturated monomer and no small molecule is eliminated, it is the polymer that is prepared by **addition polymerisation**.