Effects of Halogenated Compounds on the Rate of Radical Polymerization of Styrene

Abstract

The polymerization of styrene initiated by azobisisobutyronitrile (AIBN) were carried out at 60° C in five kinds of halogenated hydrocarbon solutions. The rates of polymerization (R_p) in solutions which contained 50 vol % styrene were increased in the following order of solvent: 1, 2-dichloroethane<chlorobenzene<bromobenzene<1, 1, 2, 2-tetrachloroethane<o-dichlorobenzene. The rates of initiation of polymerization (R_t) in solvents were determine by using benzoquinone as inhibitor and then the values of δ²(=k_t/k_p²) werecalculated from the equation: δ²=. R_t. (M)² /R_p². The values of R_t hardly changed with the nature of solvents, while the values of δ² changed markedly and showed preferably to, depend on the inverse of viscosity of the styrene-solvent system. Efficiencies of initiation of polymerization (f) in solvents were calculated from the equation, f= R_t /2 k_d(AIBN), where kd is the rate of decomposition of AIBN in solvents. There was a positive correlation between the k_d value and the dielectric constant of solvents, which was reported in previously. The values of f decreased with an increase of viscosity of the system. It was found that the polymerization of styrene in these solvents is still more sensitive than that is commonly supposed on the viscosity of system. t Solvent Effects in Radical Reactions. II.