Topology-controlled thermomechanical properties of diamond nanothread enhanced polymeric materials

Among carbon-based nanoadditive for polymeric materials, diamond nanothread (DNT) has attracted considerable interest due to its exceptional mechanical properties. However, the precise roles of DNT in the enhancement of thermomechanical properties are unknown. Here, the role of DNT with various topological structures on the glass transition temperature (Tg) of polymeric materials and the underlying mechanism of glass-rubber transition are identified utilizing molecular dynamics simulation. Interaction mechanism is discussed through density functional theory, which reveals influence of DNT topological structures on the instantaneous dipole at interface between DNT and adjacent polymer chains. Our results demonstrate that DNT with different topological structures processes variability in the enhancement of thermomechanical properties to the polymeric materials, which is related to rigidness, the dihedral angle between DNT and aromatic ring in the polymer chain, and the different mechanical interlock. The transition from glass to rubber is induced by increases in intermolecular motions, which is brought by increases in free volume at interface that are ruled by van der Waals interaction. It is also found that DNT significantly improves the Tg of epoxy nanocomposite more than other carbon-based nanoadditives. These findings reveal the thermal degradation mechanism of polymeric composite, also provide guidance for improving the reinforcing efficiency of nanomaterials in engineering applications. We anticipate our research to provide state-of-the-art theoretical approaches for the design of new nano-additives that are tailored to different reinforcement needs of polymeric composite.