Polymethyl methacrylate

Most hard contact lenses are made of this. The disadvantage of hard contacts is that it is more rigid, not oxygen-permeable and therefore doesn't allow the eye to "breathe." Also, calciumand bacteria deposits can collect on the lens if it is not cleaned regularly, causing infection.

It is soluble in toluene.

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.