A copolymer, also known as a heteropolymer, is a substance that is made from two (or more) different monomers, which usually undergo a condensation reaction with the elimination of a simple molecule, such as ammonia or water. A typical example is the condensation of 1,6-diaminohexane (hexamethylenediamine) with hexanedioic acid (adipic acid) to form nylon 6,6.


The properties of a polymeric plastic can most easily be modified if it is a copolymer of two or more different monomers, e.g., acrylonitrile-butadiene-styrene copolymer (ABS). Varying the proportions of the component monomers can preselect its properties.