# Fabrication of Self-Healable Magnetic Nanocomposites via Diels - Alder Click Chemistry
## 3 Results and Discussion
It could be further observed that the retro-DA heat flow of the hybrid system was progressively increased with increasing the IONPs-MWCNTs  
Figure 7: Wide-angle X-ray scattering (WAXS) spectra of the crosslinked PCLF/BMI/IONPs-MWCNTs hybrid samples. The solid arrows indicate the (220), (311), (400), (422), (511), and (440) crystalline reflections of the IONPs. Additionally, the dotted arrow and dashed hollow arrow indicate the (002) crystallographic plane of MWCNTs and amorphous halo of PCL, respectively. fraction, indicating that the introduction of inorganic IONPs-MWCNTs into the composites significantly increased the reactive diene and dienophile sites for DA reaction, and thus enhanced the crosslink density of the DA network. Therefore, the increased heat flow to debond the DA linkages was required. Additionally, no visible endothermic signal related to the melting point of PCL could be observed for the crosslinked PCLF based samples, indicating that the DA crosslinked structure could strongly reduce the mobility of the PCL segments and restrict the molecular chains to further crystallize, consistent with the scattering features of the WAXS results. The magnetic properties of the crosslinked PCLF/BMI/IONPs-MWCNTs hybrid system at room temperature were analyzed by using a vibrating sample magnetometer with an applied field of \(-\)10,000 Oe \(\sim\) 10,000 Oe. Shown in Figure 10 are the magnetization curves of the hybrid samples plotted as magnetic moment verses magnetic field. The insert in Figure 10 further shows the detail profiles within the field range of \(\pm\)50 Oe. For the PCLF-DA-2 sample, its magnetization hysteresis loop revealed an S-like curve and exhibited low magnetic coercivity and remanence. Upon increasing the IONPs-MWCNTs loading, both the PCLF-DA-5 and PCLF-DA-10 samples exhibited similar hysteresis loops as that of PCLF-DA-2. Therefore, these magnetic trends clearly indicated that this crosslinked PCLF/BMI/IONPs-MWCNTs hybrid system exhibited a superparamagnetic behavior and there was almost no remanent magnetization while removing the applied magnetic field. Additionally, the magnetization of the PCLF-DA-2, PCLF-DA-5 and PCLF-DA-10 samples estimated from the extreme points (\(-\)10,000 Oe and 10,000 Oe) were 700 memu/g, 1500 memu/g, and 2800 memu/g, respectively. In comparison with the pristine IONPs, the crosslinked PCLF/BMI/IONPs-MWCNTs samples revealed  
Figure 8: Thermogravimetric analysis (TGA) curves of the crosslinked PCLF/BMI/IONPs-MWCNTs hybrid samples with different loadings of IONPs-MWCNTs. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample 1** & \begin{tabular}{c} **5 wt\% Loss** \\ **Temperature (°C) 2** \\ \end{tabular} & \begin{tabular}{c} **Char Yield at** \\ **600 0°C (\%) 3** \\ \end{tabular} & \
\begin{tabular}{c} **Retro-DA Onset** \\ **Temperature (°C) 4** \\ \end{tabular} &
\begin{tabular}{c} **Retro-DA Heat** \\ **Flow (J/g) 5** \\ \end{tabular} \\ \hline PCLF-DA-0 & 362 & 16.6 & 82 & 20.5 \\ PCLF-DA-2 & 334 & 21.9 & 81 & 26.5 \\ PCLF-DA-5 & 333 & 23.6 & 83 & 28.3 \\ PCLF-DA-10 & 326 & 27.1 & 82 & 32.5 \\ \hline \hline \end{tabular}  
* Designation of crosslinked PCLF/BMI/IONPs-MWCNTs hybrid materials. [23; 5 wt\% loss temperature and char yield at 600 °C were measured from TGA analyses. [45] Retro-DA onset temperature and heat flow were measured from DSC analyses.  
\end{table} 
Table 3: Thermal properties of crosslinked PCLF/BMI/IONPs-MWCNTs hybrid samples. much lower magnetization values because of the low content of IONPs-MWCNTs in the hybrid system and the surface coverage of IONPs-MWCNTs by the non-electromagnetic PCLF polymeric layer. For the crosslinked PCLF/BMI/IONPs-MWCNTs hybrid system, its thermal reversibility related to the DA network was also investigated in solution medium (60 wt % in DMSO). Figure 11 shows  
Figure 10: Hysteresis plots of magnetization vs magnetic field for PCLF-DA-2, PCLF-DA-5, and PCLF-DA-10 crosslinked hybrid samples. The insert figure shows the detail profiles within the field range of \(\pm\)50 Oe.