文摘
Eight novel polyurea-imides were prepared by a three-step reaction procedure. First, the ureylene linkage chain-extended diamines (UCD) were synthesized by the reaction of 1 mol 2,4-diisocyanato toluene with 2 mol of a diamine in the presence of pyridine below 5°C; the condensation polymerization then took place between UCD and 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) or pyromellitic dianhydride (PMDA), forming polyurea-amic acids (PUA). The polyurea-imides (PUI) were finally obtained by imidizing the resulting PUA thermally. UCD were characterized by elemental analysis, IR, 1H-NMR and TG-DTA; PUA were investigated by IR, 1H-NMR and TG-DTA; and PUI by interfacial tension in addition to IR and TG-DTA. The results of the interfacial tension of the PUI indicate that, not only the choice of diamines and dianhydrides with different structures, but also, the introduction of ureylene linkage into polyimides are effective approaches to the modification of polyimide's interface. However, the thermal stability of the PUI is generally decreased in comparison with the corresponding homopolyimides due to the introduction of the ureylene linkage in the backbone.
