ABSTRACT
Copolymerization is a process by which two or more monomer repeat units enter the backbone chain of the polymer. This is different from the products obtained from condensation polymerization such as PET (polyethylene terepthalate) and PA (polyamide). PET is made by reacting monoethylene glycol and terepthalic acid and by removal of water molecules. The polymer backbone chain has two different repeat units. In a similar manner, hexamethylene diamine and adipic acid can be reacted together, followed by removal of water molecules to synthesize polyhexamethylene adipamide or nylon. Chain polymerizations can be carried out by allowing one monomer to polymerize to a polymer. By a free radical mechanism, the initiation, propagation, and termination reactions lead to the building of molecular weight and formation of a homopolymer with repeat units of the single monomer used as starting material. Rather than using one monomer, two or more monomers can be used as starting materials. The free radical reactions are carried out. The resulting product can be referred to as a copolymer containing more than one monomer repeat units. When more than two monomers are used, the term multicomponent copolymer can be used. The following terms can be used:
• Homopolymer: Polymer made from one monomer with one repeat unit throughout the entire backbone chain
• Copolymer: Polymer made from two monomers with two different repeat units throughout the entire backbone chain
• Terpolymer: Polymer made from three monomers with three different repeat units throughout the entire backbone chain
• Tetrapolymer: Polymer made from four monomers with four different repeat units throughout the entire backbone chain
• Multicomponent copolymer: Polymer made from more than two monomers with different repeat units throughout the entire backbone chain
An example of a homopolymer is PMMA (polymethylmethacrylate); that of copolymer is SAN (styrene-acrylonitrile); that of a terpolymer is styrene-acrylonitrilealphamethyl-styrene; and that of a tetrapolymer is polynucleotide, consisting of adenine, guanine, cytosine, and thymine.
