(a) Homopolymer means that the polymer is formed of repeating units of the same monomer whereas copolymer means polymer formed from more than one monomer.
As (NH–CHR–CO)n consists of ‘n’ number of repeating units of the same monomer ‘NH–CHR–CO’, it is a homopolymer.
(b) PVC is formed from vinyl chloride monomer through free radical mechanism. Vinyl polymerisation proceeds in three steps:
(1) Chain initiation- The radical initiator is broken into the intermediate free radicals by various means(eg. Sunlight or heat).
(2) Chain propagation – The free radicals combine with monomers to form bigger intermediate species.
(3) Chain terminating – The radical intermediates join with one another with the help of chemical bonds.
It is addition polymer as it is formed by the addition of the same monomeric unit of vinyl chloride.
(c) Bakelite is a thermoplastic. As a result they are poor conductors of electricity and subsequently they are highly heat resistant. So they are used in switches to prevent us from getting electrical shocks.
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