Synthesis and thermal-optical behaviors of non-conventional benzidine-based oligomers containing tetrasubstituted Schiff base arms

Abstract

New benzidine-based oligomers containing four Schiff base arms with terminal alkoxy chains C_nH_2n+1 (n = 6–12) were characterized by elemental, spectroscopic (UV, FT-IR, and NMR) and DFT techniques. The thermal-optical behaviors were observed using differential calorimetry and polarized optical microscope. Upon heating the molecules with n = 8, 10, and 12 exhibited endothermic peaks characteristic of the crystal-soft crystal B transition in addition to crystal-crystal subphases. It can be generalized that all oligomers showed unusual curing temperature of which the compounds with odd alkoxy chain carbon numbers possess lower curing temperatures in comparison with the analogous compounds of even parity.

Keywords:

• benzidine-based oligomers
• curing temperature
• DFT calculation
• geometric structure
• soft crystal B phase
• spectroscopic techniques

Disclosure statement

There are no conflicts to declare.

Additional information

Funding

The corresponding author (G.-Y. Yeap) would like to thank the Universiti Sains Malaysia for the RUI Grant No. 1001/PKIMIA/8011034. The DFT calculations were performed using Research Center for Computational Science, Okazaki, Japan (Project: 21-IMS-C059, 22-IMS-C059).