Formaldehyde is not present as a monomer in:

If the number average molecular weight and weight average molecular weight of a polymer are $40000$ and $60000$ respectively,the polydispersity index of the polymer will be

Match the following List-$I$ (Monomer/s) with List-$II$ (Name of the polymer) and select the correct answer:
| List-$I$ (Monomer/s) | List-$II$ (Name of the polymer) |
| :--- | :--- |
| $A$. $CF_2=CF_2$ | $I$. Neoprene |
| $B$. $NH_2(CH_2)_6NH_2, HO_2C(CH_2)_4CO_2H$ | $II$. Bakelite |
| $C$. $C_6H_5OH, HCHO$ | $III$. Teflon |
| $D$. $CH_2=CH(Cl)-CH=CH_2$ | $IV$. Nylon $6, 6$ |

Novolac is ............. .

What is copolymerization? Explain its preparation,properties and uses with an example.

Which of the following polymers is used to obtain oil seals?