Engineering intermolecular dynamic hydrogen bond interaction to regulate the tribology behaviors of shape memory polyimide

Regulating the tribological properties of shape memory polyimide and exploring their tribological mechanisms
are of great significance in promoting the application of smart lubricant materials. Herein, by engineering
intermolecular dynamic hydrogen bond interaction of shape memory polyimide, a series of isocyanate-based
polyimide-urea (PUI) shape memory copolymers were synthesized and their tribological mechanisms were
systematically investigated. The results indicated that PUI-H with multiple hydrogen bonding show significantly
enhanced tribological performance. At room temperature, the friction coefficient of PUI-H is as low as 0.127,
which is 72.4 % lower than that of PI. The wear rate is as low as 0.297 × 10?5 mm3/(N⋅m), which is 85.2 % lower
than that of PI. Further characterization results demonstrated that this excellent tribological performance
attribute to the intermolecular multiple dynamic hydrogen bond network structure, which maintain a high
degree of physical cross-linking at room temperature, whereas generate a low shear effect during the friction
process accompanied by the dissociation of hydrogen bonds afterwards promote the rapid formation of a dense
and continuous tribofilm on the surface of the steel ball, effectively reducing the coefficient of friction. Mean-
while, the dynamic reorganization of the hydrogen bonding network and the synergistic effect of π-π stacking
interactions promote the structural ordering of the molecular chain network, which strengthens the load-bearing
capacity of PUI-H, and thus significantly improves the wear resistance of the material.