Preparation and properties of polyimides containing cyano and Cardo structures

Incorporation of cyano and Cardo structures into polyimide (PI) molecular chains via structural design yielded PIs with improved thermal stability and solubility. The synthesis of novel diamino compounds (BAPMD and BACPF) enabled the preparation of two series of polyimides (PIas and PIbs), incorporating fluorene and phthalide Cardo structures, through a high-temperature one-step process using commercially available aromatic dianhydrides. The resulting amorphous PIs demonstrated exceptional solubility in solvents with low boiling points, including tetrahydrofuran (THF), dichloromethane (CH 2 Cl 2 ), and chloroform (CHCl 3 ). PIs containing the fluorene Cardo structure had glass transition temperatures ( T g ) exceeding 285 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>℃</mml:mo> </mml:mrow> </mml:math> , with thermal weight loss temperatures of 5 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>%</mml:mo> </mml:mrow> </mml:math> and 10 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>%</mml:mo> </mml:mrow> </mml:math> weight loss occurring at 505–532 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>℃</mml:mo> </mml:mrow> </mml:math> and 537–561 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>℃</mml:mo> </mml:mrow> </mml:math> , respectively, under nitrogen. In addition, both PI series exhibited low water absorption. These properties indicate that the synthesized polyimides have the potential for high-performance applications requiring thermal stability and processability.