Gama ışınlarıyla ışınlanmış naylon3 ve türevlerinin elektron spin rezonans spektroskopisi ile incelenmesi

The structural similarity between nylon3 (poly-ß-alanine) and alanine, a well known radiation dosimeter material, prompted us to conduct studying the effect of ionizing radiation on nylon3 and its derivatives. It was expected that nylon3 and its derivatives may have stable radiation-induced radicals and hence exhibit dosimetric properties.In the first part of the thesis, nylon3 (N3), 2-methyl nylon3 (2mN3) and 3-methyl nylon3 (3mN3) were prepared through base-catalyzed hydrogen transfer polymerization of corresponding monomers. Full characterization of the polymers was conducted by FTIR, NMR (1H-NMR and 13C-NMR), DSC, TGA, elemental analysis, viscosimetric analysis, and some end-group analyses. The radiation induces changes on the structure of the polymers were followed by FTIR, 1H-NMR and viscosimetry.In the second part of the thesis, the polymers were irradiated by 137Cs gamma rays in both air and nitrogen medium at room temperature. The ESR spectra of the polymers irradiated in both medium were recorded to determine the radiation induced radicals of the polymers. The changes in the ESR spectra of the samples with time were recorded in order to determine the stabilities and decay behavior of the radicals. The experimental ESR spectra of the polymers were simulated to obtain theoretical ESR spectra and its components (types of radicals). The change in the concentrations of the radicals in both medium was compared to elucidate the effect of oxygen on the decay rate of the radicals. The most important findings related to the type and decay of radicals found in nylon3 and its derivatives are the following:Nylon3 has two types of radiation induced primary radicals; a radical (Radical 1) generated by removal of hydrogen from the carbon atom next to the amide group and a radical (Radical 2) generated by removal of hydrogen from carbon atom next to the carbonyl group. The Radical 1 transforms to a relatively long lived radical (Radical 3) with unpaired electron on the oxygen atom.2-methyl nylon3 has only one type of radiation induced primary radical (Radical 2) formed by abstraction of hydrogen from the carbon atom next to the carbonyl group. This primary radical transforms to another radical (Radical 1) through disproportionation reaction and then the secondary radical transforms to a relatively long lived radical (Radical 3) with unpaired electron on the oxygen atom.3-methyl nylon3 has two types of radiation induced primary radicals; a radical (Radical 1) generated by removal of hydrogen from the carbon atom next to the amide group and a radical (Radical 2) generated by removal of methyl group from the carbon atom next to the amide group.Relative abundances of the radicals generated by irradiation of nylon3 in nitrogen were determined as R1: 32%, R2: 49% and R3: 19% by simulation of the ESR spectrum recorded immediately after irradiation. Relative abundances of the radicals generated by irradiation of 2-methyl nylon3 in nitrogen were determined as R1: 13%, R2: 76% and R3: 11% by simulation of the ESR spectrum recorded immediately after irradiation. Relative abundances of the radicals generated by irradiation of 3-methyl nylon3 in nitrogen were determined as R1: 74.7% and R2: 25.3% by simulation of the ESR spectrum recorded immediately after irradiation.Kinetic study of the decay of radicals of nylon3 and 3-methyl nylon3 showed that radicals follow apparently a first-order decay. Decay behavior of the radicals of 2-methyl nylon3 however did not reveal a clear order.Radiation chemical yields of the radicals of polymers were found to follow the following order: 2-methyl nylon3> 3-methyl nylon3 ? nylon3.