New oligomeric poly(ether-imide)s containing diphenylsilane and dibenzofuran moieties. Synthesis and characterization

A new aromatic diamine, 2,8-di(4-aminophenyl)dibenzofuran, was synthesized through the Suzuki C-C coupling reaction. This compound and an analoge diamine also based on a dibenzofuran moiety reacted with silylated-dianhydrides to yield three aromatic oligomeric poly(ether-imide)s (PEIs). The new diamine and the oligomers were characterized by elemental analysis, FT-IR, and NMR. Additionally, for the samples, solubility in an organic polar solvent was stablished and inherent viscosity values as an indirect measure of the molecular size were recovered. Some properties of PEIs were established and related to the specific structure of the repeating unit. In this sense, the rigidity/flexibility of the main chain fragments and the volume of groups bonded to silicon atom were responsible for the final properties of the polymers. All PEIs were obtained in high yield, but the inherent viscosities values of the soluble samples were low, indicating probably, low to moderated molecular sizes. The thermal decomposition temperatures measured by TGA varied from 490 to 562°C, and the Tg values ranged between 205 and 218°C. The solubility of all samples was tested in a series of common organic solvents at room temperature and at 40°C. The optical transparency in solution for the soluble samples was also determined.