Alkenes: Polymerization
Polymerization is a process by which an organic compound reacts with itself to form a high‐molecular‐weight compound composed of repeating units of the original compound. The polymerization of ethene by an ionic, or free‐radical, reagent A−B is an example.
Polymerization reactions proceed via either cationic or free‐radical mechanisms. In both processes, π bonds are converted to σ bonds, and energy is liberated. Cationic polymerization is less efficient than free‐radical polymerization due to the caustic nature of cation‐producing reagents. An example of a cation‐initiated polymerization is the reaction of ethene with sulfuric acid.
The reaction continues and gives
which finally reacts with HSO 4 − to create the polymer
The more effective free‐radical polymerization can be initiated by oxygen or other free‐radical compounds, such as peroxides. The free‐radical polymerization of ethene by an alkoxide radical is a typical reaction.
The reaction continues and gives
The reaction may end by one of two termination steps. One is the bonding of two free radicals
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