Addition polymerization

Addition polymers form by addition polymerization. Addition polymerization resembles domino blocks knocking each other over, causing a chain reaction. For such a chain reaction to occur, each monomer must contain a double bond, in which one of these two bonds is more delocalized and easy to break.

The addition reaction initiates when a free radical, an unpaired electron, breaks a double bond in order to pair with another electron. However, this creates a new unpaired electron which causes a chain reaction where the process repeats. The longer this reaction continues, the longer the polymer chain becomes. This continues until two free radicals pair up, meaning there is no unpaired electron left causing a termination reaction and the polymer chain ends.

Figure 1: The main steps of addition polymerization. The involved species are conceptualized by the magnets used for mission 1.