DETERMINATION OF GELATION DOSES OF GAMMA-IRRADIATED HYDROPHILIC POLYMERS BY DIFFERENT METHODS

Poly(acrylic acid) and pory(vinyl pyrrolidone) are hydrophilic polymer s. Poly(acrylic acid) is a polyelectrolyte which ionizes in water to p roduce an electrically conducting medium. Therefore, the gelation dose of poly(acrylic acid) can be determined by conductometric titration, simple titration and the measurement of pH. The conventional technique s of determining gelation dose are very time and material consuming es pecially for poly(acrylic acid) and subject to serious errors due to i ts electrolytic behavior. In this study, it has been shown that the ge lation dose of poly(acrylic acid) can be determined by conductimetric and titrimetric methods with NaOH and measuring pH of aqueous solution of gamma-irradiated polymer. In order to develop new, simpler and rap id methods for the determination of gelation dose of PVP, its complexa tion with gallic acid in dilute aqueous solution has been used. The co mplex formation between gallic acid and irradiated PVP in aqueous solu tions is followed by W-vis spectroscopy. The reliability of the dose v alue found, 120 kGy for poly(acrylic acid) and 140 kGy for poly(vinyl pyrrolidone), are also verified by viscometric and solubility measurem ents.