Q.Write the names of monomers of the following polymers:

Each repeat unit is analysed by locating where the monomer(s) joined and, for condensation polymers, reversing the loss of the small molecule (water) to regenerate the monomer's functional groups.

(i) $-[-NH-(CH_2)_6-NH-CO-(CH_2)_4-CO-]_n-$ — this is Nylon 6,6.

It is formed by condensation of two different bifunctional monomers:

• Hexamethylenediamine: $H_2N-(CH_2)_6-NH_2$
• Adipic acid: $HOOC-(CH_2)_4-COOH$

(ii) $-[-CO-(CH_2)_5-NH-]_n-$ — this is Nylon 6.

It is formed by the self-condensation (ring-opening polymerisation) of a single monomer:

• Caprolactam (a cyclic amide), which is equivalent to 6-aminohexanoic acid, $H_2N-(CH_2)_5-COOH$.

(iii) $-[-CF_2-CF_2-]_n-$ — this is Teflon (PTFE).

It is an addition polymer of a single monomer:

• Tetrafluoroethene: $CF_2=CF_2$, polymerised under high pressure in the presence of a free-radical or peroxide catalyst.

Recognise each repeat unit by its characteristic linkage (amide -CO-NH- for nylons, -CF2-CF2- for Teflon), then trace back to the monomer(s) — for condensation polymers add back H2O across the amide bond to recover the acid/amine or lactam.

• Writing only one monomer for Nylon 6,6 (it needs two: a diamine AND a diacid) while giving only 'caprolactam' correctly for Nylon 6 (a single monomer).
• Mixing up Nylon 6 and Nylon 6,6 repeat-unit patterns.
• Forgetting that Teflon's monomer is CF2=CF2, not CH2=CF2 or CHF=CHF.