Class 12th

15.13 

Copolymers are those polymers that consist of more than one monomeric repeating unit. Copolymerisation is a process of reacting a mixture of more than one monomeric species and form a copolymer. The copolymer can be made not only by chain growth polymerisation but by step growth polymerisation also. For example, a mixture of 1, 3 – butadiene and styrene forms Buna-S and 1-3 – butadiene and acrylonitrile form Buna-N.

15.12

In Addition polymerisation, monomers generally join together to form saturated There are three steps to chain reaction to form addition polymer, they are initiation, propagation and termination. In condensation polymerisation, functional groups of two monomers react together to release a small molecule to form a polymer. Generally, small molecules like water or HCl are released as by-products.

15.11

It is polyvinylchloride. It is a homopolymer as it is made up of the same type of repeating monomeric units.

15.10

In chemical reactions when monomer units form chains or three–dimensional networks, it is known as polymerization. Various methods of polymerization are Step-growth polymerization, Chain-growth polymerization and Condensation polymerization.

15.9 

The functionality of a monomer is defined as the number of bonds that a monomer's repeating unit forms in a polymer with other monomers. A linear polymer is formed by polymerizing if the functionality of monomer is two and is bifunctional (a thermoplastic).

15.8 Copolymers are those polymers that consist of more than one monomeric repeating unit. Some of the copolymers are Saran, Butadiene, Nitrile Rubber, Butyl Rubber, Viton and many more.

Homopolymers are those in which there is only one monomeric unit. Some of the examples of homopolymers are polypropylene, Polythene and many more.

15.7 Based on source, polymers can be classified as below:

Natural polymers: Those polymers obtained from plants and animals such as proteins, cellulose, starch and other resins.

Semi Natural polymers: Those polymers that are derivatives of natural polymers fall under this category. Cellulose Nitrate used as a propellant and in guncotton and Cellulose Acetate used in photography are prepared from Cellulose.

Synthetic polymers: Those polymers which are prepared in the laboratory are called synthetic Bakelite, Polythene, synthetic fibers and rubbers are some of its examples.

15.1

The word polymer comes from poly- (many) and -mer (part). Polymers are generally high molecular mass substances that have repeating units of smaller molecules. They may be a natural or synthetic macromolecule. The single molecular units of which a large chains are made is known as 'monomer'. These monomers generally have high molecular mass (10³- 10⁷u). Some examples of polymers are polythene, Bakelite, rubber, Buna-N and many more.

15.5

 Different types of polymers have different intermolecular forces of attraction. Elastomers or rubbers have the weakest while fibres have the strongest intermolecular forces of attraction. Plastics have intermediate intermolecular forces of attraction. Hence, the increasing order of the intermolecular forces of the given polymers is as follows:

Buna? S < polythene < Nylon 6, 6

Neoprene < polyvinyl chloride < Nylon 6

15.4