## 3 Non-Covalent Interactions
### Graphene-Based Nanocomposites  
The preparation of conjugated polymer-based nanocomposites in the presence of carbon can be achieved by in situ polymerization. This technique enables conductive polymers (CPs) to overcome their poor processability and solubility [42] by mixing the carbon materials with the monomers and then polymerizing them. [PERSON] et al. [6] reported the fabrication of nanocomposites by in situ polymerization of two different CPs, polypyrrole (PPy) and polyaniline (PANI), in the presence of graphene. They investigated the role of graphene as a nano-reinforcement filler and reported significant improvement in thermal properties with FTIR, XPS and TGA, as well as in its electrical properties as shown by a four-point probe. The graphene surface was first functionalized by amine groups covalently linked to the graphene's carbon atoms using an ethylenediamine (EDA) and dicyclohexylcarbodiimide (DCC)-based solution in THF, following its acidic treatment, which resulted in modified graphene. The grafting of the amine groups on the graphene surface was demonstrated by the presence of peaks characteristic of N-H and C-N group vibrations by FTIR, which was confirmed by XPS analysis. The nanocomposites were synthesized by in situ polymerization in three steps. First, a suspension of modified-graphene and cetyltrimethylammonium bromide (CTAB), acting as surfactant was sonicated with distilled water. In the second step, aniline or pyrrole monomers were added to the previous solution. To initiate the polymerization, ammonium persulphate (APS), which also acted as an oxidant, was sonicated with the solution from the second step. Polymerization took 24 h at 0-5 \({}^{\circ}\)C, resulting in PANI-based modified graphene (MGA) or PPy-based modified graphene (MGP) nanocomposites. a schematic diagram (Figure 10) illustrates these three steps. The use of sonication (first step) allowed the graphene sheets to be broken down, which promoted the electrostatic interactions with the monomers (second step). Then, the addition of APS initiated the polymerization from monomer molecules absorbed on the graphene sheets. The field emission scanning electron microscope (FESEM) images (Figure 11) show that regardless of the type of monomer used, the polymer covering of the graphene sheets was much more uniform for the modified graphene-based nanocomposites than for pure graphene-based nanocomposites. This may be attributed to the establishment of hydrogen bonding or \(\pi\)-\(\pi\) stacking between amino groups from the modified-graphene and the monomer molecules. Furthermore, in the case of unmodified graphene, polymerization also occurred outside the graphene, as schematically depicted in Figure 10B. Figure 10: Preparation of PANI-based modified graphene (MGA) or PPy-based modified graphene (MGP) nanocomposites using (**A**) modified graphene and (**B**) pristine graphene yielding PANI/Graphene (GA) and PPy/Graphene (GP) (Reprinted from [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Sonochemical Synthesis and Characterization of Amine-Modified Graphene/Conducting Polymer Nanocomposites. _J. Appl. Polym. Sci._**2012**, _128_, 1476–1483 [6], with permission (2020) from WILEY). It is clear that the thermal properties of nanocomposites were enhanced by the incorporation of modified graphene (the weight loss at 200 \({}^{\circ}\)C due to PPy decomposition was a little higher than in the pristine graphene-based materials, according to the TGA curves [6]). In addition, an improvement in electrical conductivity in the presence of modified graphene was shown by a four-point probe measurement system. Specifically, the MGA nanocomposites had a higher conductivity value (8.12 S/cm). The increase in conductivity may be linked to the \(\pi\)-\(\pi\) stacking between the graphene sheets and polymers as well as the uniform coating of the polymers. There are several ways to produce carbon-based composites films, but the preferred methods are the layer-by-layer (LBL) assembly technique and in situ polymerization.