## 3 Non-Covalent Interactions
### Graphene-Based Nanocomposites
The LBL assembly involves the superposition of different oppositely charged layers on a substrate, resulting in multilayered films [43]. This technique involves electrostatic interactions between the nanocarbon fillers and polymers. The fabrication of poly(vinyl alcohol) (PVA) film based on alternating deposits of the negatively charged graphene oxide (GO) and the positively charged polymer, polyethyleneimine (PEI), was reported in [44]. The functionalization of GO involved introducing negatively charged oxygen-containing groups onto its surface through the non-covalent attachment of phenoxycycloposphazene (HPTCP), a phosphorus-nitrogen compound. an important step prior to the polarity change of GO is exfoliation followed by sonication. The combination of these two steps allowed the graphene sheets to be well-separated from each other, thus preserving their properties. The self-assembly of these different layers was governed by \(\pi\)-\(\pi\) stacking interactions. In addition, one of main advantages of employing non-covalent functionalization is the very good conservation of the layered structure of graphene within the coated PVA film, which endows the PVA membrane with high flexibility. Although the LBL technique makes it possible to control the thickness of composite films and achieve uniform multilayers, this process demands a considerable amount of materials and is a lengthy process [37]. Figure 11: FESEM images of pristine graphene-based nanocomposites wrapped with (**a**) PANI and (**b**) PPy and modified graphene-based with (**c**) PANI and (**d**) PPy, at a magnification of 260.00 KX except for (**a**) 200.00 KX (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). An alternative to the production of nanocomposite films based on non-covalent interactions is the use of in situ polymerization. a polyamide-based film in the presence of a graphene/polyaniline (PANI) composite prepared by a non-covalent approach was reported in [45]. The first step was the ultrasonically assisted polymerization of the monomer aniline in the presence of exfoliated graphene under acidic conditions. Then, the in situ polymerization took place in a mixture containing the previous mixture and the monomers 4,40-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA). Finally, the resulting dispersion was cast on a glass substrate to form the graphene-polyaniline/polyimide composite film. The dispersion graphene-PANI was found to be stable as a result of the \(\pi\)-\(\pi\) interactions between the two components. As displayed by the SEM images (not shown), PANI uniformly coated the graphene surface, preventing the agglomeration of graphene sheets and resulting in a polyamide film with high electrical properties which could serve as electromagnetic interference shield. [PERSON] et al. [46] described the non-covalent decoration of graphene oxide using hyperbranched polyesters (HBP) to form GO-based epoxy resin nanocomposites. a GO dispersion was ultrasonicated into an HBP medium at 24 \({}^{\circ}\)C for one hour, and then filtered and washed, resulting in hyperbranched polyester functionalized GO (HBP-GO). Subsequently, this mixture was mixed with epoxy resin, and then cast. FTIR analysis demonstrated the adsorption of HBP into GO sheets, with a load of about \(\sim\)38% (TGA results). The non-restacking of graphene sheets was prevented by the steric hindrance between the carboxyl groups from the polyesters. Besides the good dispersion due to the \(\pi\)-\(\pi\) stacking forces, the nanocomposites showed good interfacial contact and an enhancement of mechanical properties, i.e., high microhardness, and elastic modulus.