Chemistry · Ch 15 — Introduction to Polymer Chemistry
Classification of polymers on the basis of type of different monomers
Classification of polymers on the basis of type of different monomers
Polymers can also be classified by how many distinct kinds of monomer make up their repeating units. Homopolymers contain only one type of repeating unit, usually formed from a single monomer -- polythene, polypropene, Nylon 6, polyacrylonitrile and Nylon 6,6 are all homopolymers (in some cases, as with Nylon 6,6, the single repeating unit is itself formed by first condensing two distinct small molecules into one salt, which then polymerizes). Copolymers contain two or more different types of repeating unit, formed by polymerizing two or more different monomers together in each other's presence, with the different monomer-derived units randomly sequenced along the chain -- Buna-S and B …
Worked out. Worked problem: for polyethylene (from ethylene), polyvinyl chloride (from vinyl chloride), polyisobutylene (from isobutylene), polyacrylonitrile (from acrylonitrile) and Nylon 6 (from caprolactam), each polymer comes from just one monomer, so all five are homopolymers. Nylon 6,6 also counts as a homopolymer even though it is made by condensing two different small molecules (hexamethylenediamine + adipic acid): they first combine into a single salt, hexamethylene diammonium adipate, which is the true single repeating monomer unit that then condenses further -- so there is still only one kind of repeating unit in the chain. Buna-S, by contrast, is formed directly from two distinct monomers, butadiene and styrene, polymerized together in each other's presence, and their repeating units appear randomly …