Transparent and organosoluble cardo polyimides with different trans/cis ratios of 1,4-diaminocyclohexane via aromatic nucleophilic substitution polymerization

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 ( T g ) of 275–312 °C and moderate thermal stability with 5% weight loss temperatures ( T d5% ) 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, T g of the polyimides increased as well as T d5% , while the solubility gradually decreased. The polyimide films had good optical transparency regardless of trans / cis configuration. © 2018 Society of Chemical Industry