Polybenzodiazine Aerogels: All-Nitrogen Analogues of Polybenzoxazines Synthesis, Characterization, and High-Yield Conversion to Nanoporous Carbons

Author

Vaibhav A. Edlabadkar
Saidulu Gorla
Rushi U. Soni
A. B.M.Shaheen ud Doulah
Joseph Gloriod
Samuel Hackett
Nicholas Leventis, Missouri University of Science and TechnologyFollow
Chariklia Sotiriou-Leventis, Missouri University of Science and TechnologyFollow

Abstract

Tetrahydroquinazoline (THQ) was designed as an all-nitrogen analogue of main-stream benzoxazine monomers. THQ solutions in DMF gelled at 100 °C via HCl-catalyzed ring-opening polymerization to polybenzodiazine (PBDAZ) wet gels, which were dried in an autoclave with supercritical fluid CO₂ to aerogels. These as-prepared PBDAZ-100 aerogels undergo ring-fusion aromatization at 240 °C under O₂. This oxidized form is referred to as PBDAZ-240. Chemical identification of PBDAZ-100 and PBDAZ-240 relied on consideration of all nine possible polymerization pathways, in combination with elemental analysis, infrared and solid-state 13C NMR spectroscopy, and 15N NMR spectroscopy of aerogels from the selectively 15N-enriched THQ monomer. Fully oxidized PBDAZ-240 aerogels were carbonized at 800 °C under Ar to carbon aerogels with 61% w/w yield and with retention of the nanomorphology of the parent PBDAZ-100 aerogels. Direct pyrolysis of PBDAZ-100 at 800 °C, i.e., without prior oxidation, resulted in only 40% w/w yield and complete loss of the fine nanostructure. The evolution of PBDAZ-240 aerogels along pyrolysis toward carbonization was monitored using progressively higher pyrolysis temperatures from 300 to 800 °C under Ar. Aerogels received at 600 and 800 °C (referred to as PBDAZ-600 and PBDAZ-800, respectively) had relatively high surface areas (432 and 346 m2 g-1, respectively), a significant portion of which (79% in both materials) was assigned to micropores. The new polymer aerogels, together with polybenzoxazine aerogels, comprise a suitable basis set for comparing N-rich versus O-rich porous carbons as adsorbers.

Recommended Citation

V. A. Edlabadkar et al., "Polybenzodiazine Aerogels: All-Nitrogen Analogues of Polybenzoxazines Synthesis, Characterization, and High-Yield Conversion to Nanoporous Carbons," Chemistry of Materials, American Chemical Society, Jan 2022.

The definitive version is available at https://doi.org/10.1021/acs.chemmater.2c02797

Department(s)

Chemistry

Comments

National Science Foundation, Grant CMMI-1530603

International Standard Serial Number (ISSN)

1520-5002; 0897-4756

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2023 American Chemical Society, All rights reserved.

Publication Date

01 Jan 2022