## 3 Results and Discussion
### Interface Binding Energy and Atom Distribution  
The interface binding energy in this composite system is a measure of the interaction energy between PE molecular chains and CNT, which can be expressed as  
\[E_{bind}=-E_{inter}=-[E_{PE/CNT}-(E_{CNT}+E_{PE})] \tag{5}\]  
where \(E_{bind}\), \(E_{inter}\), \(E_{PE/CNT}\), \(E_{CNT}\), and \(E_{PE}\) are the interface binding energy, the interface interaction energy, the total energy of the composite system, the energy of CNT, and the energy of PE, respectively.  
As shown in Table 1, the interaction energy between PE molecular chains and the CNT is equal to the non-bond interaction energy under both static and sheared conditions, which indicates that PE molecular chains and the CNT interact through non-bonds. Since the electrostatic interaction is small, the strong and weak interface binding energy is mostly determined by van der Waals interaction. Moreover, the interface binding energy of the sheared composite system is higher than in the static composite system.  
To further understand the effect of the orderly arrangement degree of molecular chains on interface binding energy, Figures 7 and 8 respectively show the radial distribution function (RDF) of the hydrogen (H) atoms and carbon (C) atoms of PE molecular chains in the composite system under static and sheared conditions. It can be seen that the peaks of the curves become increasingly obvious over time and with decreasing temperature. At 500 ps, the position of the peak of C atoms is 4.5 A from the surface of the CNT, and the position of the first peak of H atoms is 3.2 A from the surface of the CNT, both of which are within the range of van der Waals forces (r = 3.1-5.0 A). When the distance exceeds 5.0 A, the van der Waals interaction is weak. Furthermore, the peak value of the sheared composite system is higher than that of the static composite system, which further indicates that the orderly arrangement degree of molecular chains under shear condition is higher than under static condition. The molecular chains in the sheared composite system are arranged more closely, so more H and C atoms are close to the surface of the CNT. Therefore, the van der Waals force increases, and the interface binding energy increases correspondingly. This also indicates that the interface interaction between PE molecular chains and CNTs can be enhanced to some extent through interface crystallization.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Energy**} & \multicolumn{4}{c}{**Static**} & \multicolumn{4}{c}{**Shear**} \\ \cline{2-9}  & **PE/CNT** & **PE** & **CNT** & **E\({}_{inter}\)** & **PE/CNT** & **PE** & **CNT** & **E\({}_{inter}\)** \\ \hline \(E_{total}\) & 817,566 & \(-\)4205 & 833,057 & \(-\)11,286 & 746,293 & \(-\)73,773 & 832,769 & \(-\)12,703 \\ \(E_{non-bond}\) & \(-\)4427 & \(-\)10,839 & 17,698 & \(-\)11,286 & \(-\)14,211 & \(-\)19,322 & 17,814 & \(-\)12,703 \\ \(E_{vdW}\) & 1643 & \(-\)4552 & 17,443 & \(-\)11,248 & \(-\)5037 & \(-\)9936 & 17,556 & \(-\)12,657 \\ \(E_{electrostatic}\) & \(-\)6065 & \(-\)6286 & 259 & \(-\)38 & \(-\)9175 & \(-\)9388 & 259 & \(-\)46 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Energy of the composite system after running for 500 ps (kJ\(\cdot\)mol\({}^{-1}\)).