Methyl methacrylate reaction with phenyl radicals

The reaaions of the radicals (whether primary, secondary, solvent-derived, etc.) with monomer may not be entirely regio-or chemoselective. Reactions, such as head addition, abstraction, or aromatic substitution, often compete with tail addition. In the sections that follow, the complexities of the initiation process will be illustrated by examining the initiation of polymerization of two commercially important monomers, S and methyl methacrylate (MMA), with each of three commonly used initiators, azobisisobutyronitrile (AIBN), dibenzoyl peroxide (BPO), and di-t-butyl peroxyoxalate (DBPOX). The primary radicals formed from these three initiators are cyanoisopropyl, benzoyloxy, and t-butoxy radicals, respectively (Scheme 7). BPO and DBPOX may also afford phenyl and methyl radicals, respectively, as secondary radicals. 

TABLE 1. Copoly merization Scoping Reactions Using the Radical Ring-Opening Polymerization Monomer, 5-Methylene-2-phenyl-l,3-dioxolan-4-one, with Methyl Methacrylate... 

The elementary rate constants were calculated from ratio kp/kt, obtained from the polymerization rate and initiation rate and the ratio kp/kt, estimated from the lifetime of the radical determined by the rotating sector method. The mean lifetime of the propagating radical and derived rate constants for methacrylates are shown in Tables 7—8. The variation of the propagation rate constant for methyl methacrylate with solvents is in accordance with the result obtained by Bamford et al.2 at 25 °C. Since the largest and the smallest kp value for phenyl methacrylate differ by a factor of 1.6 and for methyl methacrylate by a factor of 1.4, the estimation of the rate constants must be performed under experimental conditions in which the accumulated error is so small as to permit a distinction of the difference. Therefore, particular attention was given to the constancy of the reaction temperature ( 0.001 °C), constancy of light source, purity of monomers and solvents, and reproducibility of observed values and to the retention of the square wave in the rotat-... 

Little has been published on techniques for achieving the homopolymerization of mono or disubstituted MA monomers (see Chapter 3). Thamm and Hensinger recently showed that y irradiation of dichloromaleic anhydride (DCMA) in benzene produced a polymer as the main product. The yield and molecular weight of the polymer increased with radiation dose. The polymer backbone contained chlorophenylsuccinic anhydride residues. It was shown that chlorophenylmaleic anhydride was produced during the reaction. Under the same conditions, dimethylmaleic anhydride (DMMA) failed to polymerize with free-radical, ionic, and UV initiation with sensitizers.Presumably, techniques may be found for the homopolymerization of chloro or phenyl-maleic anhydride. Chloromaleic anhydride (CMA) reacts with methyl radicals more readily than MA and much more readily than DCMA. " This, coupled with halogen activation and ring coplanarity, should allow CMA to be homopolymerized. It is known that CMA will copolymerize with styrene, methyl methacrylate, butadiene, cyanoacrylates, and other olefins. 

---