Polymethyl methacrylate is synthesized by radical polymerization of
methyl methacrylate.

      CH3               CH3
      |                 |
x CH2=C    →     -(-CH2-C-)-x
       |                |
       CO2CH3           CO2CH3

This type of polymerizatio reaction is usually started by a catalyst,
or an initiator such as oxygen, or a peroxide (an initiator of
free radicals). The polymerization mechanism is similar to that of
polystyrene from styrene, and polyvinyl chloride (PVC) from
vinyl chloride. The reaction can be continued until a desired
(average) chain length of the polymer is achieved. At this point, the
polymerization is stopped by addition of a free radical inhibitor.