# Fabrication of Self-Healable Magnetic Nanocomposites via Diels - Alder Click Chemistry
## 3 Results and Discussion
As shown in Figure 7, it could be observed that the WAXS profile of the PCLF-DA-0 sample revealed broad halos at 20 = 13.0\({}^{\circ}\) which corresponded to the amorphous halo of PCL, indicating that the crystallization of the PCL segments was strongly suppressed by the DA crosslinked structures. In contrast to the WAXS result for crosslinked PCLF that only showed an amorphous PCL signal, the WAXS patterns of the hybrid samples consisted of a combination of the scattering characteristics of organic and inorganic parts. It could be observed that the WAXS result of the PCLF-DA-2 sample exhibited a scattering peak at 20 = 17.1\({}^{\circ}\), which correspond to the crystalline plane of (002) associated with MWCNTs. Additionally, we could observe scattering peaks located at 20 = 20.1\({}^{\circ}\), 23.5\({}^{\circ}\), 28.4\({}^{\circ}\), 35.0\({}^{\circ}\), 37.2\({}^{\circ}\), and 40.7\({}^{\circ}\), which corresponded to the crystallographic reflections from (220), (311), (400), (422), (511), and (440) crystalline planes of IONPs, respectively. Upon increasing the fraction of IONPs-MWCNTs, the WAXS results of the hybrid samples exhibited a progressively increasing intensity of the IONPs-MWCNTs peaks, indicating the sufficient incorporation of the inorganic nanomaterials into the polymer matrix. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample 1** & **FGE/BMI Ratio** & **IONPs-MWCNTs Amount 2** \\ \hline PCLF-DA-0 & 1:1 & 0 wt\% \\ PCLF-DA-2 & 1:1 & 2 wt\% \\ PCLF-DA-5 & 1:1 & 5 wt\% \\ PCLF-DA-10 & 1:1 & 10 wt\% \\ \hline \hline \end{tabular} 1 Designation of crosslinked PCLF/BMI/IONPs-MWCNTs hybrid materials. 2 Added ratios of IONPs-MWCNTs to PCLF copolymer.  
\end{table} 
Table 2: Composition characteristics of crosslinked PCLF/BMI/IONPs-MWCNTs hybrid samples. Figure 6: FTIR spectra of pristine PCLF and PCLF-DA-5 samples. On the basis of the combined results of the TEM and WAXS analyses, a detailed investigation for the incorporation of IONPs-MWCNTs into the PCLF based polymeric matrix can now be constructed. In order to systematically study this novel crosslinked hybrid system, the thermal properties were further characterized. Figure 8 shows the TGA thermograms of the crosslinked PCLF/BMI/IONPs-MWCNTs hybrids with different compositions of IONPs-MWCNTs. The 5% weight loss temperature of PCLF-DA-0 showed a higher value than those of the other three samples since the presence of carboxylic acid functional groups on the IONPs-MWCNTs decreased the thermal stability of the hybrid samples [46]. Additionally, the char residue at 600 \({}^{\circ}\)C slightly increased with the addition of IONPs-MWCNTs, demonstrating the successful incorporation of the inorganic nanomaterials. Additionally, PCLF-DA-2, PCLF-DA-5, and PCLF-DA-10 hybrids all showed a 5% weight loss temperature higher than 325 \({}^{\circ}\)C. The weight loss temperatures and char yields of these samples are listed in Table 3. The retro-DA reaction temperatures of the hybrid samples were further analyzed by DSC measurements. As shown in Figure 9, the DSC curve of the PCLF-DA-0 sample showed a broad endothermic signal at around 140 \({}^{\circ}\)C because of the cleavage of covalent bonds composed ofuran groups of PCLF and maleimide groups of BMI via a retro-DA reaction. For the PCLF-DA-2, PCLF-DA-5, and PCLF-DA-10 hybrids, their DSC thermograms all exhibited a broad endothermic peak, which could be attributed to the combined signal from furan/maleimide, MWCNT/furan, and MWCNT/maleimide retro-DA reactions. From the significant retro-DA signals, it could be expected that these crosslinked PCLF/BMI/IONPs-MWCNTs hybrid system exhibited effective self-repairing ability imparted from the intrinsic thermal reversibility of the DA click chemistry. The retro-DA onset temperatures and heat flows of these hybrid samples were further calculated and tabulated in Table 3. Comparisons between the DSC thermograms of these measured samples showed no significant changes in the onset temperature.