A green molecular gel nanocomposite: Structure, rheological properties and tribological performance

Molecular gels are a new class of lubricants that offer many advantages over traditional lubricants. However, developing molecular gels that combine environmental sustainability with high lubrication performance remains a significant challenge. In this work, a green molecular gel lubricant using cottonseed oil as a low-cost and sustainable solvent and N -lauroyl-L-glutamic acid di-n-butylamide (GP-1) as a green gelator is developed. The thermal stability, rheological properties and lubrication performance of the gel are further enhanced by reduced graphene oxide (rGO) nanosheets. When the concentration of rGO is 1.0 wt%, the onset decomposition temperature of the gel is increased from 335 °C to 365 °C, and the storage modulus ( G′ ) is increased from ~4.05 × 10³ Pa to ~9.35 × 10 3 Pa. Correspondingly, the coefficient of friction is reduced by approximately 4.62-fold. Coarse-grained molecular dynamics simulations in combination with Fourier transform infrared spectroscopy indicate that the reinforcing effects of rGO are attributable to its physical interactions with GP-1. The interactions also promote the primary nucleation of GP-1, leading to formation of smaller GP-1 fiber network domains that help distribute GP-1 nanofibers more homogeneously in the gel. The gel network restructuring and reinforcement by rGO may work together to contribute to the high lubrication performance of the gel nanocomposite. Apart from the sustainability design of this molecular gel, the mechanistic insights provide some guidance on the selection of nano-additives for designing a high-performance molecular gel lubricant.