1   Explain the terms polymer and monomer.

Solution :

Polymers are high molecular mass macromolecules composed of repeating structural units derived from monomers. Polymers have a high molecular mass $(10^ 3 - 10^7 u)$. In a polymer, various monomer units are joined by strong covalent bonds. Polymers can be natural as well as synthetic. Polythene, rubber, and nylon 6,6 are examples of polymers. Monomers are simple, reactive molecules that combine with each other in large numbers through covalent bonds to give rise to polymers. For example, ethene, propene, styrene, vinyl chloride.

2   What are natural and synthetic polymers? Give two examples of each type.

Solution :

Natural polymers are polymers that are found in nature. They are formed by plants and animals. Examples include protein, cellulose, starch, etc. Synthetic polymers are polymers made by human beings. Examples include plastic (polythene), synthetic fibres (nylon 6,6), synthetic rubber (Buna - S).

3   Distinguish between the terms homopolymer and copolymer and give an example of each.

Solution :

$\textbf{Homopolymer}$$\\$ The polymers that are formed by the the polymerization of a single monomer are Known as homopolymers. In other words, the repeating units of homopolymers are derived only from one monomer. For example, Polythene is homopolymer of ethene.$\\$ $\\$ $\textbf{Copolymers}$$\\$ The polymers whose repeating units are derived from two types of monomers are known as copolymers. For example, buna-s is a copolymer of 1, 3-butadine and styrene.

4   How do you explain the functionality of a monomer?

Solution :

The functionality of a monomer is the number of binding sites that is/are present in that monomer.For example, the functionality of monomers such as ethene and propene is one and that of 1, 3- butadiene and adipic acid is two.

5   Define the term polymerization.

Solution :

Polymerization is the process of forming high molecular mass $(10^3 - 10 ^7 u)$ macromolecules,which consist of repeating structural units derived from monomers. In a polymer, various monomer units are joined by strong covalent bonds.

6   Is $(-NH-CHR-CO-)_n$ a homopolymer or copolymer ?

Solution :

$(-NH-CHR-CO-)_n$is a homopolymer, because it is obtained from a single monomer unit, $NH_ 2 - CHR - COOH$

7   In which classes, the polymers are classified on the basis of molecular forces?

Solution :

On the basis of magnitude of intermolecular forces present in polymers, they are classified into the following groups:$\\$ (i) Elastomers$\\$ (ii) Fibres$\\$ (iii) Thermoplastic polymers$\\$ (iv) Thermosetting polymers

8   How can you differentiate between addition and condensation polymerisation?

Solution :

Addition polymerization is the process of repeated addition of monomers, possessing double or triple bonds to form polymers. For example, polythene is formed by addition polymerization of ethene.

Condensation polymerization is the process of formation of polymers by repeated condensation reactions between two different bi-functional or tri-functional monomers. A small molecule such as water or hydrogen chloride is eliminated in each condensation. For example, nylon 6,6is formed by condensation polymerization of hexamethylenediamine and adipic acid.

9   Explain the term copolymerization and give two examples.

Solution :

Nylon 6, 6 is also a copolymer formed by hexamethylenediamine and adipic acid.

The polymers from two or more different monomeric units is called copolymerization. Multiple units of each monomer are present in a copolymer. The process of forming polymer Buna -S from 1, 3-butadiene and styrene is an example of copolymerization

10   Write the free radical mechanism for the polymerization of ethene.

Solution :

Polymerization of ethene to polythene consists of heating or exposing to light, a mixture of ethene with a small amount of benzoyal peroxide as the initiator. The reaction involved in this process is given below: