Influence of poor solvents in radical polymerizations of methyl methacrylate

Abstract

Radical polymerizations of methyl methacrylate (MMA) were carried out in the presence of poor solvents for poly(methyl methacrylate) (PMMA) at 60°C. At 40 vol% or above of n-hexane and at 50 vol% of cyclohexane, the solutions became turbid during polymerization and the polymers precipitated. But the precipitates were not observed in methanol (≤50 vol%). The kinetic order of the initiator was 0.5 when no precipitate was observed, but it became less than 0.5 when the precipitate was present. Under homogeneous conditions, the values of (1+x)kt/kp2were determined from the relations between 1/Pn and Rp, and varied with the viscosity of the system. When a precipitate was observed, kt/kp2could not be determined. It is concluded that when a precipitate is observed, the propagating radical grows large enough to precipitate by itself and the termination rate decreases. © 1989 The Society of Polymer Science, Japan.