## 2 Covalent Interactions
### CNT-Based Nanocomposites
#### 2.1.2 Grafting-From through Inverse Emulsion Polymerization  
Multiple studies have described the introduction of CNT into a polyaniline (PANI) matrix, since PANI is one of the most common electrically conductive polymers. When combined with carbon nanotubes (CNT), the resulting composites lead to considerable enhancement in terms of their mechanical, electric and optoelectrical properties [3]. PANI is a frequent choice because of its ease of synthesis, versatile properties, and its low-cost monomer [26]. In situ inverse emulsion polymerization is one of the most widely employed modes of fabrication of these nanocomposites. [PERSON] et al. [27] developed nanocomposites based on PANI in the presence of MWCNTs. The surfactant Camphor-10-sulfonic acid (\(\beta\)) (CSA) was dissolved in chloroform to which a distilled aniline solution and ammonium persulfate (APS) were added, followed by MWCNTs, either in situ (before polymerization) or ex situ (after polymerization) and then were sonicated. The morphology evidenced by Cryo-TEM showed that the MWCNT nanotubes were well-coated by PANI, resulting in a core-shell structure for both PANI/ MWCNT in situ and ex situ with an average diameter of \(\sim\)50 nm for the in situ. The dispersions displayed long term stability (several months) and low resistivity, thus confirming the formation of MWCNT-PANI interactions. [PERSON] et al. [28] developed a new, rapid in situ dynamic inverse emulsion polymerization process under sonication resulting in stable nanocomposite PANI/MWCNTs in which MWCNTs were coated by PANI, leading to uniform PANI/ MWCNT tubes with an average diameter of \(\sim\)37 nm, as shown in high resolution scanning electron microscope (HRSEM) images (Figure 8). The aqueous phase containing the APS radical initiator was added in the continuous phase containing aniline (monomer), dodecyl benzene sulfonic acid (DBSA, dopant), MWCNTs and toluene (solvent). The presence of MWCNTs enhanced the mechanical properties and electrical conductivity. They also tested other types of single-walled and double-walled carbon nanotubes, all of which were coated with PANI at a thickness of 11-34 nm [18]. a two-point probe technique showed that the PANI/CNT composites exhibited high film resistivity and light transparency and a decrease in haze as the film's thickness decreased [18]. Figure 8: High resolution scanning electron microscopy (HRSEM) image of MWCNT/PANI nanocomposites prepared by ultrasonically induced inverse emulsion polymerization (Reprinted from [PERSON]; [PERSON]; [PERSON]; [PERSON] Fabrication of Composite Polyaniline/CNT Nanofibers Using an Ultrasonically Assisted Dynamic Inverse Emulsion Polymerization Technique. _Polym. Adv. Technol._**2009**, _21_, 150–152 [28], with permission (2020) from WILEY). [PERSON] et al. [29] also carried out in situ inverse emulsion polymerization followed by either precipitation-filtration or a drop-cast step to produce nanocomposite PANI/CNT within a styrene-isoprene-styrene (SIS) block copolymer elastomeric matrix, as depicted in Figure 9. They showed that the precipitation-filtration method was significantly more efficient for the generation of a continuous well-organized three-dimensional CNT network [29]. [PERSON] et al. [30] also produced a core-shell nanostructure in which CNT was wrapped by PANI as seen in the HRSEM images and the fact that elastomeric 'islands\" of SIS block copolymer were created (Figure 9). The use of PANI enabled the CNT to be well separated from each other, thus forming a stable dispersion when prevented from agglomerating (fewer Van der Waals interactions). The percolation threshold was low (\(\sim\)0.4 by weight) due to the formation of these islands. They also showed that adding CNT considerably enhanced the mechanical properties which could later be tuned as a function of the CNT filler [30]. a very high Young's modulus was reported, along with a decrease in strain at break for CNT loadings between 3 and 7 wt%, whereas lower mechanical properties were obtained for higher loadings.