Designing of molecular architecture, synthesis and properties of the next generation of state-of-the-art high-performance thermoplastic fluoro-poly(ether amide)s, (6F-PEA), fluoro-poly(ether amide-imide)s (6F-PEAI), and their co-polymers

Abstract

A new generation of high-performance polymers for the advanced industrial, aerospace and defense engineering applications are being investigated in the academic and industrial research institutions throughout the world. Fluoro-polyimides (6F-PI) are one such sub-class of high-performance polyimide polymers. In the last 25 years a number of fluoro-polyimides have been reported but only a handful of them have been commercialized. This paper describes the 6F-polyimide chemistry-based designed molecular architectures and synthesis of two series of next generation of heat stable thermoplastic polymer compositions having di-ether diamines moieties, such as fluoro-poly(ether amide) (6F-PA) and fluoro-poly(ether amide-imide) (6F-PEAI) using the novel state-of-the-art 2-(3,4′-carboxy anhydrophenyl-2(4-carboxyphenyl) hexafluoropropane (6F-TMA) and 2,2′-bis(4-carboxyphenyl) hexafluoropropane (6F-DAc) monomers. Their co-polymers: fluoro-copoly(ether amide-(ether imide))s (6F-co(PEA-PEI)), fluoro-copoly(ether amide-(ether amide-imide))s (6F-co(PEA-PEAI)) and fluoro-copoly(ether amide-imide-(ether imide))s (6F-co(PEAI-PEI)) were also designed and synthesized using 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydrides (6FDA). Solution, thermal, electrical, chemical resistance, thermo-oxidative and hydrolytic stabilities, etc., properties of two series of polymers and co-polymers were analyzed. These 6F-polymers possess moderate to high glass transition temperature (Tg). The Tg values of co-polymers were re-confirmed by the Fox-Vora equation. These polymers showed excellent resistance toward thermo-oxidative degradation in isothermal heating at temperature 300 °C for 300 h. Most of these 6F-PEAI, 6F-PEAI, 6F-co(PEA-PEI), 6F-co(PEA-PEAI) and 6F-co(PEA-PEAI) polymers also shown to have low moisture uptake at 100% relative humidity at 50 °C over 100 h. The dielectric constant (ɛ′) of these polymers in addition to experimentally measuring, were also estimated by the additive group contribution calculation using mathematical equations defined by the Lorentz–Lorenz's theory and the Vogel's theory, and by Vora–Wang equations, respectively. Their dielectric constants (ɛ′ < 3.15) were lower than the control film samples of commercially available non-fluorinated polymers, such as unfilled polyamide-imide Torlon®, poly(ether imide) ULTEM®1000, and polyimides: Kapton®H and Upilex®S. The amorphous nature of these designed 6F-polymers renders them readily processable into films, sheets, etc., molded articles.