The influence of alkyl groups at ortho-position of amino group on the structure and properties of polyimides

• Published in: Polymer bulletin (Berlin, Germany) Vol. 80; no. 9; pp. 9881 - 9897
• Main Authors: Zhao, Yixin, Wang, Mingliang, Wang, Xi, Yi, Chunwang, Su, Shengpei
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2023; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Charge transfer; Chemistry; Chemistry and Materials Science; Complex Fluids and Microfluidics; Electromagnetic absorption; Ethanol; Glass transition temperature; Hydrocarbons; Modulus of elasticity; Molecular chains; Optical properties; Organic Chemistry; Original Paper; Phenylenediamine; Physical Chemistry; Polyimide resins; Polymer Sciences; Rigidity; Soft and Granular Matter; Tensile strength; Electron-donating; Rigidity; Structure; Properties; Polyimides
• ISSN: 0170-0839; 1436-2449
• DOI: 10.1007/s00289-022-04537-z

A series of polyimides (PIs) using four kinds of m -phenylenediamine monomers containing different substituent groups at the ortho -position of the amino group was synthesized. Furthermore, these polyimides with variable rotational freedom of the imide bond and the rigidity of the polyimides molecular chain were used to investigate the influence of these alkyl groups on the structure and properties of PIs. The results of property tests revealed the effects of these substituent groups on the properties of PIs. The glass transition temperatures ( T g s) and tensile strengths of PIs have increased due to the decrease of the rotational freedom of the imide bond and the increased rigidity of the polyimides molecular chain. Due to the weakening of the intermolecular charge-transfer (CT) interactions caused by the substituent groups, the solubility of PIs has been improved. All the PIs with alkyl groups exhibit greater tensile strength and higher Young's modulus because the introduction of alkyl groups can increase the rigidity of the molecular chain. While due to the electron-donating property of the alkyl groups, the intramolecular CT interactions in the PI molecule become stronger making the PIs with alkyl groups exhibit stronger visible light absorption capability.