Analysis of the kinetics of soluble polyimide formation by the thermal imidization of polyamic acids in amide solvents with allowance for the side reaction of anhydride group hydrolysisстатья
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Аннотация:A kinetic analysis of the process aimed at preparing soluble polyimide by the thermalimidization of a prepolymer, polyamic acid (PAA), in a dimethylacetamide solution ina temperature range of 120—160 С was carried out. The scheme including elementary reactions of imidization, synthesis, and decomposition of PAA, as well as the reversible sidereaction of hydrolysis of anhydride groups with water released during imidization was usedin the analysis. The PAA was synthesized by the low-temperature polycondensation of2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and 2,2-bis(4-aminophenoxyphenyl)propane (BAPP). The rate constants of hydrolysis of anhydridegroups and dehydration of phthalic acid fragments were determined experimentally formodel compounds: phthalic anhydride and phthalic acid. The experimentally found rateconstants of elementary reactions of imidization, decay, and synthesis of PAA of the samechemical structure and in the same temperature range determined by the authors earlierwere also used in the calculations. The solution of the system of kinetic equations wasperformed by the numerical integration using the Maple 17 software. The developedmodel makes it possible to calculate the dependence of the change in the number averagemolecular weight of the formed polyimide. According to the calculation results, the initialPAA concentration aff ects the character of the dependence: the higher the initial concentration of PAA, the more noticeable the role of the side reaction of hydrolysis of terminalanhydride groups, which reduces the rate of increasing average degree of polymerization. Перевод. Акт экспертизы акт от 29.12.2022