Nitrogen-based thermoset polymers have many industrial applications (for example, in composites), but are difficult to recycle or rework. We report that a simple one-pot, low-temperature polycondensation between paraformaldehyde and 4,4'-oxydianiline (ODA) forms hemiaminal dynamic covalent networks (HDCNs) that can further cyclize at high temperatures to form poly(hexahydrotriazine)s (PHTs). Both materials are strong thermosetting polymers, and the PHTs exhibited very high Young's  moduli (up to ~14.0 gigapascals and up to 20 gigapascals GPa when reinforced with  surface-treated carbon nanotubes), excellent solvent resistance, and resistance to environmental stress cracking. However, both HDCNs and PHTs could be digested at low pH (<2) to recover the bisaniline monomers. When  poly(ethylene glycol) diamine monomers were used to form HDCNs, elastic organogels formed that exhibited self-healing properties.

Recyclable, strong thermosets, and organogels via paraformaldehyde condensation with diamines

248th National Meeting (2014)

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