Covalent functionalization of fluorinated graphene through activation of dormant radicals for water-based lubricants. (15th October 2020) - Fan, Kun
Abstract: Targeted covalent functionalization of graphene derivatives and simultaneously preserving their intrinsic structure and property are an underexplored, urgent and challenging task in two-dimensional chemistry. Herein, we develop a novel and facile method to achieve lossless covalent functionalization of fluorinated graphene (FG) through activating dormant radicals, derived from stabilization from conjugation effect of surrounding aromatic regions/fluorine atoms and particular two-dimensional skeleton. The activated radicals under definite temperature initiate acrylic acid (AA) to be grafted onto FG surface without any catalyst, completely different from traditional nucleophilic substitution (SN ) reaction through sacrificing fluorocarbon bonds. Compared to destructive self-lubricating ability of FG-PEI from SN reaction, obtained FG-AA improves water dispersibility of hydrophobic FG and simultaneously maintains intrinsic self-lubricating ability with limited commensurate stacking and week interlayer interactions. Therefore, FG-AA presents excellent tribological performance as water-based lubricant additive, regarded as eco-friendly and sustainable system, whose friction coefficient and wear rate have about 66% and 82% decrease compared to that of FG-PEI, respectively. Moreover, taking advantage of such FG chemistry, the activated radicals and originally reactive fluorocarbon bonds also offer two non-interfering routes to implement stepwise double functionalization of graphene. Designing this strategy in mind expands the applications of FG in aqueous environment and enriches graphene chemistry. Graphical abstract: Lossless covalent functionalization of fluorinated graphene through activating dormant radicals toward water-based lubrication and double functionalization. Image 1