Macromolecular Rapid Communications
Macromolecular Rapid Communications
5 years ago

Control of Head/Tail Isomeric Structure in Polyimide and Isomerism-Derived Difference in Molecular Packing and Properties

Control of Head/Tail Isomeric Structure in Polyimide and Isomerism-Derived Difference in Molecular Packing and Properties
Xiangyang Liu, Xu Wang, Yu Dai, Longbo Luo, Yihao Yuan
Two sequence isomeric poly(amic acid)s (PAAs) are successfully synthesized from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and unsymmetrical 5(6)-amino-2-(4-aminobenzene) benzimidazole (PABZ). The syntheses are based on the site-selective reactivity of head/tail amino groups of PABZ and solubility differences of PABZ in good solvent (dimethyl sulfoxide, DMSO) and poor solvent (N-methyl-2-pyrrolidone, NMP). The proton nuclear magnetic resonance (1H-NMR) results reveal that the content of head tail–head tail (HTHT) bonding units in PAA-DMSO (PAA synthesized in DMSO) is 37%, while this content increases to 54% in PAA-NMP (PAA synthesized in NMP). The wide-angle X-ray diffraction (WAXD) results indicate polyimide (PI)-NMP film with high HTHT content exhibits a semicrystalline structure, while PI-DMSO film is amorphous. Moreover, PI-NMP also shows higher in-plane orientation than PI-DMSO. The ordered molecular packing and higher in-plane orientation of PI-NMP lead to an increase in mechanical properties and a decrease in in-plane thermal expansion coefficient. Two sequence isomeric poly(amic acid)s and polyimides are successfully synthesized based on the site-selective reactivity of head/tail amino groups of 5(6)-amino-2-(4-aminobenzene) benzimidazole (PABZ) and solubility differences of PABZ in good solvent and poor solvent. Polyimide obtained in poor solvent shows a higher content of head tail–head tail sequence units and exhibits a crystalline structure.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/marc.201700404

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