As just mentioned, a polymer is a large macromolecule. The word “polymer” can be broken down into the Greek components: poly (many) + mer (part). “One part” would then be called a monomer, “two parts” would be a dimer, “three parts” a trimer, “a few parts” is an oligomer. Polymers can be made of a single repeating unit, over and over, there can be many different monomers in a polymer, you can have ordered repeats, random repeats, there are infinite combinations, and we will talk about the structure of the polymer in detail.
To create a polymer, imagine linking together a bunch of monomer units by sequentially reacting each monomer together. Table 1.1 in the textbook shows examples of chemical structures of common monomers and the polymers that result from their polymerization. Notice the nomenclature for how we name the polymer from the monomer, also pay attention to the notation used for describing the repeat unit of the polymer, which is the structure appearing in the brackets [ ]. Let’s use styrene as an example (Figure 1.5).
Styrene is the name of the monomer, but the repeat unit is the part that is “repeated” (in the brackets) that make up the polymer. The repeat unit is not necessarily the same as the monomer; a repeat unit can be made from multiple monomers for example. If the number of atoms, and hence the molecular weight, of the monomer is the same as the repeat unit, then we call this a polyaddition polymerization. However, the number of atoms in the repeat unit is not always the same as the monomer, if there are chemical byproducts of the polymerization reaction (and we would call this a polycondensation polymerization). A good example of this would be nylon 6,6 produced from the polymerization of hexamethylenediamine and adipic acid (Figure 1.6). Notice that the repeat unit of nylon 6,6 is a combination of both monomers, and that some atoms were lost during the polymerization so that the chemical structure of the repeat unit is not just the simple addition of both monomers; we have lost H2O in this reaction. Can you identify the bond formed between the hexamethylenediamine and the adipic acid in the nylon polymer?
