Thermally Stable, Organosoluble, and Colorless Poly(ether imide)s Having Ortho‐Linked Aromatic Units in the Main Chain and Trifluoromethyl Pendent Groups

Abstract

AbstractSummary: A novel series of aromatic poly(ether imide)s (PEIs) IVa–h containing ortho‐linked aromatic units and pendent trifluoromethyl (CF3) groups were prepared from 2,3‐bis(3,4‐dicarboxyphenoxy)naphthalene dianhydride (I) with various CF3‐substituted aromatic bis(ether amine)s IIa–h via a conventional two‐stage process including ring‐opening polyaddition to form the poly(amic acid)s followed by either chemical or thermal imidization to the PEIs. The inherent viscosities of PEIs IVa–h were in the range of 0.43–0.86 dL · g−1 that corresponded to weight‐average and number‐average molecular weights (by gel permeation chromatography) of 36 000–73 000 and 23 000–51 000, respectively. All the IV series were highly soluble in several organic solvents and could be solution‐cast into transparent, flexible, and strong films. These films were essentially colorless; their cut‐off wavelengths were between 368 and 377 nm and a very low b* value (a yellowness index) ranging from 4.1 to 5.5. They had useful levels of thermal stability associated with moderately high‐glass transition temperatures (208–281 °C), 10% weight‐loss temperatures in excess of 492 °C, and char yields at 800 °C in nitrogen higher than 51%. They also showed low water uptakes of 0.25–0.48% and low dielectric constants of 3.06–3.67 at 10 kHz. For a comparative study, a series of structurally similar, non‐fluorinated PEIs Va–h from dianhydride I and bis(ether amine)s II′a–h were also prepared and characterized.A novel series of aromatic poly(ether imide)s (PEIs)IVa–h.magnified imageA novel series of aromatic poly(ether imide)s (PEIs)IVa–h.