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Abstract
Pyrogallol is polymerized using the method developed by El-Garf et.a!. The effect of different factors on the yield is also studied. These factors are polymerization temperature, polymerization time and the molar ratio of monomer and catalysts. It is shown that the yield increases by increasing polymerization time and polymerization temperature. The effect of molar ratio of the monomer and the catalyst shows that increasing the molar ratio ofFeCh.6H20 trom 1 to 2 does not considerably increase the percentage yield as it increases from 83.36% to 89.80%. The polymer used in this study is that prepared to give 89.9% yield.
The polymer is studied by infrared which shows that its structure is poly (1,2,3 trihydroxy¬4,5 phenylene) which resembles a zigzag structure. The mechanism of the polymerization reaction is proposed to be radical-cationic polymerization. The polymer also is found to be insoluble in common organic solvents. The X-ray diffraction study of the polymer confirms the presence of phenyl ring and that the polymer is amorphous and that the repeat unit consists of one phenyl ring. The elemental analysis also confirms the structure of the repeat unit.
DT A in nitrogen atmosphere shows three principal exothermic peaks due to decomposition. On this basis the mechanism of decomposition is proposed by using bond energy. Generally the DTA does not show endothermic melting peaks which means that the polymer does not melt up to 10000 C. The exothermic peaks do not show crystallization because there are no phase transitions and these peaks are due to decomposition ranges in the DTG curves. The DTG shows a peak at 51.30 C which begins at 300 C and ends at 990 C which is due to evaporation of water of humidity. TGA also shows that at temperature interval of 147.60 C to 6000 C the percentage weight loss due to decomposition is found to be 49.355%. The weight loss from room temperature to 10000 C is 76.351% after subtraction of percentage of evaporation of water of humidity and the percentage residue of the polymer is 23.649%.
The properties of the prepared polymer are studied as the electrical properties and radiation shielding properties.
The electrical conductivity of the pure polymer and polymer coated with polystyrene is studied and it is shown that the electrical conductivity increases with increasing temperature which is in the range of semiconductors (103 _10-10 ohm-I.cm-I). Coated polymer by 0.212% polystyrene has also semiconducting properties. Although the later has relatively a lower electrical conductivity but it is still within the range of semiconducting properties. The mechanism of electrical conduction has been proposed. The band theory is excluded and the hopping mechanism is proposed according to which current is transferred by activation jumps of carriers from one polyconjugated region to another over the dielectric barriers created by the disordered (unconjugated structure). The generation and movement of carriers inside the polyconjugated regions requires no activation energy. With increasing temperature the carrier concentration does not change but the mobility increases exponentially. The electrical conductivity of poly pyrogallol polymer is compared with other polymers in the literature and is found to have an electrical conductivity lower than polychloropyridine, polyacrylonitrile, polycyanic acid and poly(copper phthalocyanine) and greater than poly( 4,4’ -diethynyl diphenyl oxide).