writer：Yongmei Tang, Lan Li, Kai Ma, Guofei Chen,* Wei Wang, Xingzhong Fang.*
keywords：polyimides, transparent, cardo, aromatic nucleophilic substitution, trans/cis configuration
source：期刊
specific source：Polym. Int.
Issue time：2018年

Two series of cardo polyimides were prepared from1,4-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-offwavelengths of 350–355nm andmoderatemechanical properties. The different properties of the polymers caused by trans and cis configurations of 1,4-diaminocyclohexanewere also investigated. Itwas found that with an increasing content of

trans configuration of 1,4-diaminocyclohexane in the polyimide backbone, Tg of the polyimides increased aswell as Td5%,while the solubility gradually decreased. The polyimide films had good optical transparency regardless of trans/cis configuration.