Panasonic (Czechia)

Abstract Polyimides are a group of polymers with excellent thermal and mechanical properties. However, generally, they exhibit brown coloration due to charge transfer interactions between diamine donor and dianhydride acceptor moieties. In this study, semi-alicyclic polyimides derived from cyclohexane tetracarboxylic dianhydride and 4,4′-oxydianiline were prepared using a two-step method, where the imidization step proceeded via a chemical route. The effects of the catalyst type (quinoline, triethylamine, and 1,4-diazabicyclo(2.2.2)octane (DABCO)) and reaction temperature (120, 140, and 160 °C) on the imidization process were evaluated using infrared spectroscopy and nuclear magnetic resonance spectroscopy. The prepared polyimides' thermal, mechanical, and optical properties were compared with those synthesized via standard thermal imidization. Polyimide films possessing favorable mechanical properties, thermal stability, and good optical transparency were prepared via a simple preparation route based on chemical imidization using the triethylamine catalyst at the reaction temperature of 160 °C, which was shown to be a promising way for the PI preparation on an industrial scale. Graphical abstract

Centripetal chromophores based on the s -triazine core with tuneable properties and excellent two-photon absorption properties were used for the construction of high-quality and well-transparent emissive polyimide films.

Two novel emissive chromophores based on triphenylamine and carbazole have been designed, prepared and further utilized as comonomers towards end-capped emissive colourless polyimides.

Abstract Aromatic polyimides have become popular due to their exceptional properties, including superior thermal resistance. However, these materials have a strong absorption in the UV–vis region, which limits their applications, including those for a space environment. The effect of trifluoromethyl groups in aromatic and semi-aromatic polyimide structures on their final characteristics, specifically optical, thermal, and mechanical properties, solar absorptance, emissivity, and outgassing, was investigated to develop high-performance materials suitable for space applications. As the starting dianhydride monomers, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) were used to react with different diamine monomers, specifically 4,4′-oxydianiline (ODA), 4,4′-oxybis[3-(trifluoromethyl)aniline] (6FODA), 1,4-bis(4-aminophenoxy)benzene (APB), and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB). It was found that trifluoromethyl groups positively affected the thermal and optical properties of polyimide films. The thermal stability of the 6FDA-based polyimides exceeded 500 °C. The fully fluorinated polyimide films of poly(6FDA-6FODA) and poly(6FDA-6FAPB) exhibited transmittance at 400 nm ( T 400 ) of 53% and 44%, respectively, whereas their partly fluorinated analogues of poly(6FDA-ODA) and poly (6FDA-APB) showed T 400 of 3% and 10%, respectively. Moreover, the presence of trifluoromethyl groups improved outgassing results, where the fully aromatic poly(6FDA-6FAPB) film achieved the best performance. In contrast to the CHDA-based polyimides, all 6FDA-based polyimides achieved the total mass loss values (TML) < 1, which meets one of the essential requirements for space applications. Graphical abstract