THE EFFECT OF PHENOLS AND AROMATIC THIOLS ON THE POLYMERIZATION OF METHYL METHACRYLATE

Abstract

Chain transfer constants of a number of phenols in the polymerization of methyl methacrylate have been determined. They are small compared with the corresponding transfer constants with styrene, a maximum value of 0.0026 being observed with pyrogallol. Three deuterated phenols do not have a measurable effect on the rate and degree of polymerization, showing that attack takes place mainly at the O—H group.The aromatic thiols investigated have transfer constants in the range 2.6 to 7.4. They cause only slight retardation of polymerization, and efficiencies of reinitiation by aromatic thiol radicals are estimated to be at least 95%. The transfer constants of meta-substituted thiols do not differ greatly from that of benzenethiol showing that inductive effects are small. A wider range of reactivities is observed with the para-substituted thiols, indicating the existence of small but significant resonance effects.