Molecular-Pillar-Supported Functionalized Reduced Graphene-Oxide for Energy Efficient Lubrication

Molecular-pillar-supported basal plane of reduced graphene oxide (rGO) is fabricated by polymerizing polyaniline (PANI). In the presence of poly(ethylene glycol) (PEG200), the gamma-radiolysis is used for modifying the functionalization and improving the structural symmetry of PANI and PEG grafted rGO (PANI-PEG-g-rGO). The PANI is covalently and noncovalently grafted onto the surface of the graphene sheets. Carboxyl groups of rGO are linked to the nitrogen atoms in the PANI backbone and an accompanying noncovalent interaction between alkyl chains of grafted PANI and hydrooxylated rGO is formed. Raman and Fourier transform infra-red results confirm existence of stretching vibrations of benzenoid and quinonoid rings in PANI-PEG-g-rGO-functionalized composite, indicating grafting between PANI and rGO through pi-pi interaction. Furthermore, PEG-functionalization through hydrogen bonding with rGO is confirmed when hydroxyl group from the rGO combines with oxygen of PEG. X-ray photoelectron spectroscopy reveals significant increase in carbon, while loading PANI network with rGO followed by gamma-irradiation. Antifriction and antiwear properties of graphene nanocomposite are considerably enhanced to 68.4% and 48%, respectively, as compared to pristine PEG. The unique lubrication properties are explained by PEG functionalized molecular PANI-pillar structure across basal plane of rGO.