# Fabrication of Self-Healable Magnetic Nanocomposites via Diels - Alder Click Chemistry
## 3 Results and Discussion
These results clearly provided the evidence that MWCNTs could interact with the furan groups of PCLF via a DA reaction, resulting in a homogeneous dispersion of IONPs-MWCNTs within the copolymer matrix. This outcome demonstrated that DA reaction could be efficiently applied to modify the surfaces of MWCNTs by using furan group as a diene. Our result also bears resemblance to that of a previous report wherein poly(furfuryl methacrylate) (PFMA) containing furfuryl functional group was covalently bonded onto the surfaces of MWCNTs via a DA reaction, thus strongly enhancing the miscibility between the MWCNTs and the polymer matrix [44]. The formation of these DA structures attached to the surfaces of MWCNTs could be confirmed by monitoring the solubility of the hybrids in solvent medium. Figure 4a shows the image of dispersion condition in DMSO for the PCLF/IONPs-MWCNTs DA adducts. We observed that the hybrids could be uniformly dispersed in DMSO solvent after a brief sonication process and the dispersity of the mixture exhibited superior dispersion stability. As the well-dispersed suspension system was heated at 160 \({}^{\circ}\)C for over 5 h, the inorganic IONPs-MWCNTs gradually precipitated from the dispersion due to the occurrence of detachment of PCLF from MWCNTs surfaces via a retro-DA reaction, as shown in Figure 4b. In addition to the MWCNT/furan DA reaction, it has been also reported that MWCNT could serve as a \"diene\" and react with maleimide (dienophile) through the DA mechanism [45]. Therefore, the addition of BMI into the hybrid system to fabricate crosslinked PCLF/BMI/IONPs-MWCNTs hybrid material could provide additional support for the inorganic IONPs-MWCNTs and maintain their uniform distribution in the polymer matrix. For the crosslinked PCLF/BMI/IONPs-MWCNTs hybrid system developed in this study, a schematic illustration showing its thermo-reversible DA network formed from furan/maleimide, MWCNT/furan, and MWCNT/maleimide combinations is shown in Figure 5. Additionally, the designations and compositional characteristics of the prepared hybrid samples were tabulated in Table 2. The DA and retro-DA reactions of the PCLF/BMI/IONPs-MWCNTs hybrid system could also analyzed by using FTIR measurements (shown in Figure 6). In comparison with the characteristic profile of pristine PCLF, the spectrum of the crosslinked PCLF/BMI/IONPs-MWCNTs sample (PCLF-DA-5) exhibited additional 1773 and 1708 cm\({}^{-1}\) peaks associated with the C=C stretching of DA adducts and C=C stretching vibration of BMI, respectively. This signal change clearly indicated the formation of DA adducts via a DA reaction. For the PCLF-DA-5 sample, the peak at 756 cm\({}^{-1}\) corresponding to furfuryl moiety also disappeared, which again confirmed the occurrence of DA reaction that change the original furan rings in pristine PCLF [30]. Figure 3: **(a)** TEM micrograph of acid-treated multiwalled carbon nanotubes (MWCNTs). **(b)** TEM micrograph of the iron oxide nanoparticles-multiwalled carbon nanotubes (IONPs-MWCNTs) hybrid. For this sample, its corresponding high magnification TEM image is further shown in **(c)**. The TEM image in **(d)** shows the morphology of PCLF/IONPs-MWCNTs sample containing 10 wt% IONPs-MWCNTs, indicating a good dispersion of IONPs-MWCNTs in the polymer matrix. **(e)** EDX spectrum of IONPs-MWCNTs hybrid deposited on a silicon wafer. Figure 4: (a) Dispersion condition of the PCLF/IONPs-MWCNTs Diels–Alder (DA) adducts in DMSO. (b) Dispersion condition of the PCLF/IONPs-MWCNTs DA adducts in DMSO after heating at 160 \({}^{\circ}\)C for 5 h.  
Figure 5: Schematic representation of the thermo-reversible DA network formed fromfuran/maleimide, MWCNT/furan, and MWCNT/maleimide combinations. We subsequently examined the crystallography features of the hybrid system by using WAXS measurements.