Highly phenylated polyimides containing 4,4′-diphenylether moiety

A new aromatic diamine, 2,2′,6,6′-tetraphenyl-4,4′-oxydianiline (4PhODA, 4), has been synthesized by oxidation, bromination, Suzuki coupling and reduction of 4,4′-oxydianiline (4,4′-ODA). Highly phenylated polyimides PI7a-f were prepared from diamine 4 and six commercially available aromatic dianhydrides by one-step method. The inherent viscosity of these polyimides ranged from 0.33 to 0.91 dL/g, measured in a 0.5 g/dL of NMP or m-cresol solution at 30 °C. These highly phenylated polyimides showed excellent solubility. Especially, polyimide PI7a derived from the rigid pyromellitic dianhydride (PMDA) was soluble in DMAc, NMP at room temperature, and in DMF, chloroform, and m-cresol at 60 °C. Transparent, flexible and tough films can be obtained by casting from their NMP or m-cresol solutions. They exhibited good thermal stability, except PI7a containing pyromellitic diimide and PI7f containing nathphalenic diimide (Tg > 350 °C), their glass transition temperatures measured by thermal mechanical analysis (TMA) ranged from 298 to 340 °C. The decomposition temperatures at 5% weight loss under nitrogen were 506-542 °C. They also showed excellent mechanical properties. The enhanced solubility combined with good thermal stability could allow these phenylated polyimides to be further functionalized by various aromatic electrophilic substitutions on four phenyl rings for polyelectrolyte applications.