Polymerization of Methyl Methacrylate Initiated by Chlorocarbonylbis (triphenylphosphine)iridium(I) and Organic Halides

Abstract

The polymerization of methyl methacrylate (MMA) initiated by chlorocarbonylbis(triphenylphosphine)iridium(I) (Ir complex) and organic halides in benzene was studied. The effect of combination of organic halides with Jr complex on the polymerization was studied, and it has been found that carbon tetrachloride (CCl₄), carbon tetrabromide, and bromoform show the polymerization ability. On the basis of the kinetic studies of the polymerization of MMA in benzene initiated by Jr complex and CCl₄ (low concentration), the rate of polymerization (Rp) was expressed by the following equation:
Rp=k[Ir complex]^0.5. [CCl₄]^0.5. [MMA] ^1.0
The apparent overall activation energy for the MMA polymerization by the use of this initiator was estimated to be 17.6 kcal/mol. The composition curve of the copolymerization of styrene with MMA by the use of this initiator agrees with that of the radical polymerization; the polymerization of MMA is inhibited by 1, 1-diphenyl-2-picrylhydrazyl and p-benzoquinone. On the basis, of the above results, the polymerization of MMA by the use of this initiator was found to proceed through a free-radical mechanism.