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摘要
In order to study the dissociation behavior of polyacrylic acid (PAAH) with different molecular weight in aqueous solution as well as the difference between the dissociation behavior of polyelectrolyte (polyacrylic acid) and small molecular weak electrolyte (acrylic acid (AAH) and acetic acid (HAc)), this paper prepared polyacrylic acid with polymerization degree in the range of 300~2 000 by precipitation polymerization method. The pH value of polyacrylic acid, acrylic acid and acetic acid aqueous solution was measured by pH meter to determine the dissociation behavior of electrolyte. Then from the thermodynamic point of view and Flory-Huggins lattice model, the paper derived the dissociation equilibrium equation of electrolyte in the dissociation process. The results show that the dissociation behavior of polyacrylic acid in aqueous solution is independent of the degree of polymerization. By simplifying the dissociation equilibrium equation, the calculation formula of the traditional equilibrium constant Kα was obtained and given its exact physical meaning: the relative strength parameter of the interaction energy of the dissociation hydration effect of electrolyte aqueous solution in the dissociation process. By substituting the data into the dissociation equilibrium equation, it is found that there are two kinds of molar ionization hydration energies ?Es in polyelectrolyte and small molecule weak electrolyte, in the low concentration region and the high concentration region, respectively. This is the reason why acrylic acid, acetic acid and polyacrylic acid deviate from the traditional equilibrium constant Kα theoretical line in the low concentration region. ? 2023 South China University of Technology.
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