SYNTHESIS AND CHARACTERIZATION OF POLY(1-ADAMANTYL METHACRYLATE) - EFFECTS OF THE ADAMANTYL GROUP ON RADICAL POLYMERIZATION KINETICS AND THERMAL-PROPERTIES OF THE POLYMER

Radical polymerization of 1-adamantyl methacrylate (AdMA) and 3,5-dimethyl-1-adamantyl methacrylate (DMAdMA) with 2,2'-azobisisobutyronitrile in benzene at 60-degrees-C was investigated kinetically. The introduction of the bulky adamantyl groups increased its polymerization rate and the molecular weight of the resulting polymer, compared with those for other methacrylates, e.g., methyl, tert-butyl, and cyclohexyl esters. It was ascribed to decrease in the termination rate, resulting in increase of the concentration of its propagating polymer radical at a stationary state. It was confirmed directly by observation of ESR spectra of the propagating radical and verified that the concentration of the polymer radical was ca. 10(-6) mol/L, being higher than that for ordinary polymerization. The conformational structure of the poly(AdMA) radical was also discussed from the hyperfine coupling constants in the spectrum. Subsequently, the tacticity was examined by NMR spectroscopy and compared with those for poly(methyl methacrylate). It was revealed that the polymers bearing adamantyl esters showed extremely high glass transition temperatures, and the effect of the tacticity was also investigated. From thermogravimetric analysis in a nitrogen stream, the decomposition temperatures of these adamantyl-containing polymers were quite high in spite of the tertiary alkyl ester groups.