Molecular dynamics simulations to study the tensile behavior of hyperbranched polyamide-modified nanocellulose

To address the limited understanding of the micromechanical behavior in hyperbranched polyamide (HBPA)-modified nanocellulose systems, this study employed molecular dynamics simulations using GROMACS to systematically examine the effects of HBPA concentration, water content, and strain rate on tensile properties. Molecular models with varying parameters were constructed and analyzed for stress-strain response, hydrogen bonding evolution, structural root mean square deviation (RMSD), and key intramolecular energy terms (bond, angle, and torsion). In addition, a comparison was made between simulations and experiments under dry and wet conditions. The results show that water content is the most critical influencing factor, and high water content (41.7 wt%) can reduce the yield strength by about 70%. HBPA enhances toughness via a dynamic, reconstructable hydrogen-bond network enabling efficient energy dissipation. An optimal concentration of ~5 wt% balances interfacial bonding and self-aggregation. High strain rates suppress molecular rearrangement, dissipating energy through bond/angle deformation, whereas low rates allow dissipation via conformational relaxation and hydrogen-bond reformation. Water-induced plasticization is quantitatively attributed to competitive hydrogen bonding and a lubricating effect that reduces interchain friction. The simulation and experimental verification under dry and wet conditions indicate that the key of simulation prediction lies in reproducing the process history of the experimental sample as accurately as possible.