Radiation-induced, solid-state polymerization of derivatives of methacrylic acid. IX. Electron spin resonance and product analysis study of the gamma radiolysis of methacrylic acid, barium methacrylate and their saturated analogues, isobutyric acid and ba

Methacrylic acid and barium methacrylate polymerize in the solid state during and after gamma irradiation. Previous ESR studies have indicated a free radical chain mechanism initiated by radical, particularly H atom, addition to the C=C bond. The radiation chemical yields of small molecular products are now reported and correlated with the ESR spectra and yields of molecular products from the saturated analogues, isobutyric acid and barium isobutyrate, in order to provide a detailed mechanism for the radiolysis. The ESR spectrum of barium isobutyrate at -196°C was similar to that of isobutyric acid and is attributed to (i) isobutyrate radical CH3-Ċ(CH3)COO-; (ii) isobutyrate anion radical [CH3-CH(CH3)COO-]-; and (iii) isopropyl radical CH3-Ċ(CH3)H. Conversion of radicals (ii) and (iii) into (i) occurred on warming and second-order decay of (i) was measured at higher temperatures. For isobutyric acid irradiated at 0°C, G(CO2)=5.4, which is compatible with values for n-carboxylic acids, but in marked disagreement with G(CO2)=14.4 for isobutyric acid reported by Johnsen.(11) Water was proven to be a significant radiolysis product. CO2 was the major product from methacrylic acid and barium methacrylate, but in lower yields than from the isobutyrates; the other products were propyne, hydrogen, water, propylene, carbon monoxide and methane, all in relatively low yield

Radiation-Induced, Solid-State Polymerization of Derivatives of Methacrylic Acid. XL Aspects of the Polymerization of Methacrylic Acid by y-lrradiation

Aspects of the radiation-induced polymerization of methacrylic acid in the crystalline state have been investigated and utilized to evaluate the mechanism of polymerization. In particular, results for post-irradiation polymerization at 0°C after radiation doses of 0.1 to 2.0 Mrad support the concepts of Lando and Semen that chain initiation essentially all commences at the same time, that chain propagation continues without termination, and that termination of nonpropagating radicals proceeds simultaneously

Structural Aspects of Polymerization in Crystalline Ionic Monomers: Comparison of Barium Methacrylate Monohydrate and Anhydrate

Barium methacrylate monohydrate, Ba2 +[CH2=C(CH3)COO] 2H2O, maybe readily polymerized in the crystalline state by γ-irradiation. However, except under special conditions, there is negligible polymer produced when anhydrous barium methacrylate is exposed to γ-irradiation. The differences in polymeriz-ability are considered in relation to the detailed spatial arrangements of the methacrylate molecules and molecular mobility associated with development of disorder