Synthesis and characterization of polyimides based on 3,6-diphenylpyromellitic dianhydride

Due to their insolubility and high glass transition temperatures (Tg's), aromatic polyimides have traditionally been processed in the form of their poly(amic acid) precursors. Considerable research over the past decade has led to several systems that can be melt and/or solution processed. The objective of this research was the preparation of a series of soluble, aromatic polyimides that would display high moduli. In particular, 3,6-diphenylpyromellitic dianhydride was to be synthesized and polymerized with a series of aromatic diamines. It was postulated that the phenyl groups would afford solubility while the pyromellitic moiety would maintain chain rigidity.