Studies on polymers containing functional groups. VI. Kinetics of the polymerization and copolymerization behaviors of o-hydroxystyrene

Some kinetic studies were made of the homopolymerization of o-hydroxystyrene and its copolymerization behavior with styrene and methyl methacrylate in tetrahydrofuran using azobisisobutyronitrile as initiator were done. The rate of polymerization experimentally obtained is given by R_p = KM]I]^0.72. Accordingly, it is likely that the growing chain radicals are terminated not only by mutual termination but also by a chain-transfer mechanism, the latter occupying a considerable portion. The latter is mostly attributed to the transfer to monomer, i.e., C_m for o-hydroxystyrene was 1.3 × 10^?2. Some transfer mechanisms were assumed, although it is difficult to elucidate the mechanism in detail, owing to its complexity. Effects of solvent on the rate of polymerization were examined, dioxane, methyl ethyl ketone, ethanol, and tetrahydrofuran being used. However, no differences were found among the solvents. The apparent activation energy of polymerization was found to be 21.5 kcal./mole. Monomer reactivity ratios and Alfrey-Price Q–e values for o-hydroxystyrene were determined. The Q–e values (Q = 1.41, e = ?1.13) are rather similar to those of p-methoxystyrene. Thus, the e value for o-hydroxystyrene is more negative than that for styrene.