Viscoelastic Covalent Organic Nanotube Fabric via Macroscopic Entanglement
Kalipada Koner, Susobhan Das, Shibani Mohata, Nghia Tuan Duong, Yusuke Nishiyama, Sharath Kandambeth, Suvendu Karak, C. Malla Reddy, Rahul Banerjee
Abstract
Covalent organic nanotubes (CONTs) are one-dimensional porous frameworks constructed from organic building blocks via dynamic covalent chemistry. CONTs are synthesized as insoluble powder that restricts their potential applications. The judicious selection of 2,2′-bipyridine-5,5′-dicarbaldehyde and tetraaminotriptycene as building blocks for TAT-BPy CONTs has led to constructing flexible yet robust and self-standing fabric up to 3 μm thickness. The TAT-BPy CONTs and TAT-BPy CONT fabric have been characterized by solid-state one-dimensional (1D) 13 C CP-MAS, two-dimensional (2D) 13 C– 1 H correlation NMR, 2D 1 H– 1 H DQ–SQ NMR, and 2D 14 N– 1 H correlation NMR spectroscopy. The mechanism of fabric formation has been established by using high-resolution transmission electron microscopy and scanning electron microscopy techniques. The as-synthesized viscoelastic TAT-BPy CONT fabric exhibits high mechanical strength with a reduced modulus ( E r ) of 8 (±3) GPa and hardness ( H ) of 0.6 (±0.3) GPa. Interestingly, the viscoelastic fabric shows time-dependent elastic depth recovery up to 50–70%.