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Abstract: Two series of cardo polyimides were prepared from 1,4‐bis(4‐fluorophthalimide)cyclohexane with different trans/cis ratios and phenolphthalein/o‐cresolphthalein via aromatic nucleophilic substitution reaction. The inherent viscosities of the synthesized polymers were found to be 0.55–0.66 dL g−1 in N,N′‐dimethylacetamide. The cardo polyimides showed excellent solubility in organic solvents, high glass transition temperatures (Tg) of 275–312 °C and moderate thermal stability with 5% weight loss temperatures (Td5%) of 415–441 °C in nitrogen and 370–436 °C in air. The polyimide films exhibited high optical transparency with cut‐off wavelengths of 350–355 nm and moderate mechanical properties. The different properties of the polymers caused by trans and cis configurations of 1,4‐diaminocyclohexane were also investigated. It was found that with an increasing content of trans configuration of 1,4‐diaminocyclohexane in the polyimide backbone, Tg of the polyimides increased as well as Td5%, while the solubility gradually decreased. The polyimide films had good optical transparency regardless of trans/cis configuration. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A series of cardo based asymmetric polyimides containing bulky rigid naphthalimide and phthalimide groups were prepared from asymmetric monomer bishaloimide and bisphenols by solution polycondensation. Bishalo(naphthalimide-phthalimide) monomers containing different terminal leaving groups (Cl, F, NO2) were synthesized, and the reactivity difference of these monomerswas compared for the successful synthesis of polyimides. The inherent viscosities of the polyimideswere in the range 0.51-0.60 dL g-1 in N-methyl-2-pyrrolidone at 30 °C. These polyimides demonstrated good organosolubility and mechanical properties with tensile strengths of 93-120MPa, tensile moduli of 3.5-5.3GPa and elongations at break of 2.8%-4.3%. The polyimides showed high glass transition temperatures (Tg) ranging from330 to 363 °C. The10%weight loss (T10%) of asymmetric polyimides reached 436-500 °C in nitrogen and 417-476 °C in air. The water uptake of the polyimides was in the range 0.35%-0.72%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two series of cardo polyimides with high T g s and high transparency were prepared. • A new method to prepare PIs with alicyclic diamine to avoid salt formation was provided. • The DMPF base polyimide PI-IIa displayed high thermal properties with T g of 350 ℃ and high transparency with transmittance of 86% at 400 nm. Two series of transparent cardo polyimides (PIs) derived from bisphenol fluorenes and 1,4-bis(4-fluorophthalimide)cyclohexanes (BFCH) with different ratios of trans- and cis - 1,4-diaminocyclohexane were prepared via aromatic nucleophilic substitution. These PIs exhibited high glass transition temperatures (T g s) of 271–352 °C, 5% weight loss temperatures (T d 5%) of 400–433 °C in nitrogen, mechanical properties of tensile strengths of 62–107 MPa, tensile moduli of 3.0–4.4 GPa and elongations at break of 1.7–4.5% and great solubility in a variety of organic solvents. These PI films appeared excellent optical transparency, which displayed the cut-off wavelengths from 323 to 355 nm and high transmittance at 450 nm with more than 85 %. The steric effects of different substituent groups on bisphenol fluorene and different ratios of trans / cis configuration were also investigated. [ABSTRACT FROM AUTHOR]