Bulk Polymerization of Methyl Methacrylate Initiated by AIBN (Reaction 3) Freshly distilled methyl methacrylate monomer (4) is treated with a small amount of azobisisobutyronitrile (in an approximately 200:1 monomerlinitiator weight ratio) and a trace of methacrylic acid. The mixture is then allowed to polymerize at about 40°C during one day to give a transparent, glassy polymer (5). The poly- merization can be effected in a mold (or the bottom of a glass beaker), in which case poly(methyl methacrylate) may be added to the initial reaction mixture to raise the viscosity. Sheets of poly(methyl methacrylate) glass can be prepared by the use of a mold of two glass plates clamped together and separated by a rub- ber gasket (see Chapter 20) 58 Free-Radical Polymerization Chapter 3