High-Performance Degradable Poly(hexahydrotriazine)s and Their Potential for Tribological Applications

The isomeric poly(hexahydrotriazine)s (PHTs) were prepared, based on their hemiaminal dynamic covalent networks via a facile method at 50 °C, through 1,3-bis(4-aminophenoxy)-benzene (TPE-R) and 1,4-bis(4-aminophenoxy)-benzene (TPE-Q) with formaldehyde. The influence of chain isomerism on thermal stability, mechanical properties, tribological properties, and the degradation rate of PHTs was investigated. The advantage of (TPE-Q)-PHTs compared with that of (TPE-R)-PHTs is that they possessed a higher glass transition temperature (Tg) of 187 °C, a higher Yang’s modulus of 10.7 GPa, and rapid degradation rate. Additionally, the (TPE-Q)-PHTs exhibited outstanding self-lubricating performance as compared to (TPE-Q)-PHTs because the para-connecting isomers showed lower surface energy, lower surface roughness, and higher hardness that effectively weakened the bonding force between friction pairs. Overall, the study of PHTs facilitates their practical application of energy conservation and environmental protection in the tribological industry.