Application of the Spin Trapping Technique to Radical Polymerization. 21. Vinyl Polymerization with the N-Hydroxysuccinimide/Acetylacetonato Metal Chelate System

Abstract Some combinations of N-hydroxysuccinimide (NHS) and acetyl-acetonato metal chelates were found to induce radical polymerization. A kinetic study on the polymerization of methyl methacrylate (MMA) was performed by using as initiator the NHS/trisacetyl-acetonatomanganese(III) (Mn(acac)3) system, which can initiate the polymerization effectively even at room temperature. The overall activation energy of polymerization was very low (9.1 kcal/mol). The polymerization rate (Rp) was expressed by where the initiator concentration was varied by fixing [NHS]/[Mn(acac)3] = 2. Rp showed a maximum when [Mn(acac)3] was changed while keeping [NHS] constant. Further, a spin trapping study revealed that the primary propagating radical was trapped even in the system containing only a small amount of monomer (1.6 × 10−2 mol/L). These results indicate that a complex from NHS and Mn(acac)3 with a very high stability constant plays an important role in the generation of initiating radicals, and that the monomer partic...