3 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

You might also like
Never Miss Important Research

Researcher is an app designed by academics, for academics. Create a personalised feed in two minutes.
Choose from over 15,000 academics journals covering ten research areas then let Researcher deliver you papers tailored to your interests each day.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.