A large number of simple molecules called monomers combine together to form a macromolecule called a polymer. Each polymer has a repeating structural unit. If the repeating structural unit is derived from one type of monomer molecules, the polymer is said to be a homopolymer and if it is derived from two or more different types of monomer molecules, the polymer is said to be  a copolymer. Both homopolymers and copolymer may be formed either by addition or condensation reactions. Alkenes and dienes polymerize by addition (chain growth)mechanism involving carbocations, carbanions or free radical intermediates. Dienes (chloroprene, isoprene, etc.) polymerize by 1,4-addition mechanism to give cis- or trans- polymers. Natural rubber is however, cis-polyisoprene. Natural rubber is quite soft and tacky but these properties can be improved by a process called vulcanization. In contrast, bifunctional monomer molecules undergo, condensation or step-growth polymerization. Polymers which can be heated and reshaped as many times as desired are called thermoplastics while those which can be heated only once to give a particular shape are called thermosetting polymers.

Which polymer is formed by the monomer Chloroprene?

Neoprene