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- Title
Control of Head/Tail Isomeric Structure in Polyimide and Isomerism-Derived Difference in Molecular Packing and Properties.
- Authors
Luo, Longbo; Dai, Yu; Yuan, Yihao; Wang, Xu; Liu, Xiangyang
- Abstract
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.
- Subjects
POLYIMIDES; ISOMERISM; MOLECULAR structure; AMIC acids; PROTON magnetic resonance
- Publication
Macromolecular Rapid Communications, 2017, Vol 38, Issue 23, pn/a
- ISSN
1022-1336
- Publication type
Article
- DOI
10.1002/marc.201700404