Polymerization
Polymerization is the process where the polymers are made. They can be divided into two main categories: step-growth and addition polymerisation.
In step-growth polymerization, which at first was called condensation polymerization, two different functional groups such as a carboxy acid react with a hydroxyl group to form an ester bond. This is illustrated in Figure 6 on the following page.
Addition polymerization include radical, ionic and coordination polymerization where electrons from double-bond containing compounds are employed to form polymers. These feed stock compounds, often of vinyl type, are called monomers, e.g. vinyl chloride CH2=CHCl.
Whereas addition polymerization has the three distinctive steps; initiation, progression and termination that quickly generates a polymer, the step-growth polymerization progresses steadily where the starting compounds first are consumed, forming dimers, then trimers and so on. Hence, the step-growth polymerization needs to reach high conversion for true polymers to be formed whereas addition polymerization may be halted at any time to harvest the formed full-length polymers.