Question

Write the names and structures of the monomers of the following polymers:
(i) Buna – S (ii) Neoprene

Answer 1

A monomer refers to the molecule having the capability to form a chemical bond with other molecules present in a long chain. While, a polymer is a complex molecule which generally refers to a chain of several numbers of monomers. In simpler terms, we can say that monomers refer to the building blocks of polymers.

Complete answer:
i) Buna-S name has been derived from Bu - butadiene and S – stands for styrene. Hence, it is derived from two monomers, i.e. butadiene and styrene and thus, it is also known as styrene butadiene rubber. It is usually obtained by the polymerization of Buta-1,3-diene and styrene in the ratio of 3:1 in the presence of sodium. Hence, it is called butadiene-styrene copolymer. It is generally utilised for the making of automobile tyres and footwear.
(ii) On the other hand, Neoprene is formed through a chemical reaction which utilises chloroprene, and as a resultant, polychloroprene chips are left behind. It is generally prepared through the free radical polymerization of chloroprene. Thus, it is also known as polychloroprene. It is employed as an insulator, for the manufacturing of hoses, belts, gaskets, etc.
The names and structures of the monomers of Buna – S and Neoprene are shown in the following table:

S.No.	Polymer	Monomer	Structure of monomer
(i)	Buna - S	1, 3-butadiene
	Styrene (vinylbenzene)
(ii)	Neoprene	Chloroprene (2-chlorobuta-1,3-diene)

Note: Buna - S is a random co-polymer which is produced by the emulsion polymerization of a mixture of butadiene and styrene (1:3) in the presence of peroxide catalyst at a temperature of 5 degree Celsius. Therefore the product formed is called cold rubber. And, the rubber obtained is also known as Styrene butadiene rubber (SBR). It is then vulcanized with sulphur. Moreover, the rubber is slightly inferior in quality to natural rubber in its physical characteristics.
Neoprene is a synthetic rubber produced by the polymerization of chloroprene. It possesses good chemical stability as well as maintains quite good flexibility over a wider range of temperature.