Radical Polymerization of Dimethylstyrenes and their Copolymerization with Methyl Methacrylate

Abstract

The polymerization of 2, 4-, 2, 5-, 2, 6-, 3, 4- and 3, 5-dimethylstyrene (DMS) and their copolymerization with methyl methacrylate (MMA) were carried out by using azobisisobuty ronitrile (AIBN) as an initiator. The rates of polymerization (R_p) were expressed by the following equations: 2, 4- D M Sand 2, 5-DMS at 60°C: R_p=const. [AIBN]^0.4[Monomer]^1.4, and 3, 4-DMS and 3, 5-DMS at 60°C: R_p= const.[AIBN]^0.4[Monomer]^1.2.
The polymer of 2, 6-DMS was scarcely obtained by the use of AIBN at 60°C. In the copolymerization, the order of Q values of the o, o' -disubstituted group is one-tenth, which belongs to unconjugated type. The interplanar angles between ethylenic bond and benzene ring in the o-substituted groups were calculated on the basis of the ultraviolet absorption spectra. The result shows that the lowering of Q values of o, o'-disubstituted group is not attributed to the bulkiness of o-substituted methyl groups but to the inhibition of conjugation, resulting from planar twist between ethylenic bond and benzene ring, and that relative reactivity of 2, 4-, 2, 5 or 2, 6-DMS correlates to the interplanar angle between ethylenic bond and benzene ring.