Molecular assembly of graphene oxide for self-healing lubrication architectures in thermoplastic phenolic resin nanocomposites

Abstract

Despite the exceptional lubricity of graphene oxide (GO) for polymer composites, achieving its full tribological potential remains constrained by nanofiller aggregation due to the strong π-π interactions and poor interfacial compatibility with the matrices. To address these challenges, a molecular assembly strategy was proposed and hence an atomic-level uniformly dispersed GO in thermoplastic phenolic resin (TPR) was achieved through an in-situ polymerization of phenol monomers with pre-grafted GO nanosheets, overcoming aggregation via covalent bonding between GO’s oxygen-containing groups (–COOH, –OH) and phenolic –OH groups. Remarkably, incorporating just 0.5 wt% GO reduced the friction coefficient by 50 % (from 0.4 to 0.2) and implanting 1.0 wt% GO decreased the wear rate by more than 2 orders of magnitude (from 1.8 × 10⁻⁵ mm³/Nm to 1.2 × 10⁻⁷ mm³/Nm) when sliding against bearing steel in dry friction. It was attributed that GO nanosheets underwent tribochemistry at the sliding interface, forming a robust nano-lubricity tribofilm with a thickness of about 150 nm and composed of aligned GO layers chemically anchored with hydroxylated iron (FeOOH). This interfacial architecture enhanced the tribofilm’s robustness and self-healing capacity, therefore improving wear resistance of the nanocomposites extraordinarily.