Influence of Number and Strength of Hydrogen Bonds\non Fracture Property and Microscopic Mechanisms of Associative Hydrogen-Bonded\nPolymers via Molecular Dynamics Simulation

A coarse-grained\nmodel combining the acceptor–hydrogen–donor\n3-body potential is first developed in this work to explore the fracture\nproperty and microscopic mechanisms of associative hydrogen-bonded\npolymers (AHBPs). Next, a triaxial deformation mode is performed to\nreveal that the fracture toughness of AHBPs initially improves and\nthen is reduced as the number of active groups increases. By characterizing\nthe stress decomposition, the strong hydrogen bond (HB) network improves\nthe maximum stress but reduces the elongation. The destructive process\nof the HB network is described by quantifying the broken number and\nreduced energy of HBs. Interestingly, the strength of a single HB\nfirst decreases and then rises with strain. The initial decrease is\nmainly caused by the disruption of strong/moderate HBs, while the\nfollowing rise is due to the further breakage of weak HBs and partial\nrecovery of strong/moderate HBs. Meanwhile, the formed clusters of\nHBs due to the self-attraction act as the physical cross-links, whose\nevolution process is recorded by analyzing their number and size.\nFollowing it, the orientation degree and asphericity factor are calculated\nwith strain to reflect the change in chain configuration, which is\ninfluenced by the HB network. Subsequently, the nucleation and growth\nprocess of voids is quantified. More than 90% of voids are nucleated\nin the polymer region, while others are in the HB region, which can\nbe proved by the local elastic modulus and snapshots. The growth and\ncoalescence rate of the voids can be suppressed by the strong HB network.\nFinally, the fracture toughness of AHBPs exhibits a continuous increase\nwith improving strength of HBs due to the strong HB network. In summary,\nour work presents a clear and novel comprehension of the fracture\nproperty of AHBPs at the molecular scale.