Formation of the chain microstructure in the synthesis of adamantane-containing copolyimides in molten benzoic acid

Abstract

High-resolution ¹³C NMR spectroscopy was applied to study the chain microstructure of copolyimides obtained at 140 °C by one-pot high-temperature polycondensation in molten benzoic acid from 2,2-propylidene-bis(4-phenylene-4´-oxyphthalic acid) dianhydride (DA, intermonomer) and two comonomers, 1,3-bis(2-aminoethyl)adamantane (ADA) and 9,9-bis(4aminophenyl)fluorene, varying the order of introduction of components into the system. The experimentally found value of chain microheterogeneity coefficient determined from the ¹³C NMR data is in a good agreement with the values theoretically calculated using the mathematical model developed earlier by the authors and the kinetic data for the model reactions of acylation of amino groups and imidization of amido acid fragments. An ADA—DA-2,2-hexafluoropropylidene-bis(phthalic acid) dianhydride system provides another example of the principal possibility of varying orders of introduction of components to control the chain microstructure of copolyimides.