Synthesis and properties of cardo-type polyimides containing hydroxyl groups for application in specific detection of fluoride ion

Abstract

Here, four cardo-type polyimides containing hydroxyl groups have been successfully synthesized by one-step solution polymerization of a hydroxyl-containing fluorene diamine monomer and various commercial dianhydride monomers. The obtained PIs with high molecular weights were readily soluble in many polar solvents. Simultaneously, they still maintain the excellent thermal stability (the 5% and 10% weight loss temperatures over 480 °C and 510 °C in nitrogen, respectively) and the high glass transition temperatures (Tgs, 342–442 °C). Furthermore, PI films show high tensile strength (>78 MPa) and relatively high optical transparency (over 82% at 500 nm), except PI-4. Utilizing that hydroxyl group in PI chain is able to form H-bond interaction with F−, these hydroxyl-containing PIs in DMSO solution are successfully applied as colorimetric chemosensors for detection of F− with high selectivity and sensitivity. Finally, the PI film chemosensors is also used for visual and reversible sensing of F−, which enables them to be a fast and portable test kit for visible detection of F−.