Quantitative Structure-Properties Relationships and Molecular Dynamic Simulations of Some Lubricant Additives (LAs)

The degradation of this zinc-dialkyl-dithiophosphate (ZDDP), at a temperature less than 246K often leads to the release of phosphorus, sulphur, and zinc which are indirectly responsible for the emission of poisonous gas from the exhaust pipe of the motor cars. Four QSPR mathematical models were generated from 39 structures of lubricant additives (LAs) and the structural features were found to corresponds to the coefficients of; internal correlation (R2 ) of 0.95, adjusted squared correlation (R2 adj) of 0.94, Cross-validation (Q2cv) of 0.90, and the external validation (R2 pred) of 0.54. The model suggests that new LAs with improved onset temperatures (Tonset) could be designed by interpreting and increasing the value of the molecular descriptor such as IC5 (Information Content index/neighborhood symmetry of 5-order) and Ve (V total size index/weighted by Sanderson electronegativity) and at the same time decreasing the values of RDF080m (Radial Distribution Function-080/weighted by mass), RDF110m (Radial Distribution Function-110/weighted by mass), P2v (2nd component shape directional WHIM index/weighted by Van der Waals volume) and R1e+ (R maximal autocorrelation of lag 1/weighted by Sanderson electronegativity). Moreover, the LAs with an experimental onset temperature of 351.6K agreed with the predicted onset temperature of 351.7K13a. And was also in agreement with the result of molecular dynamics simulations in which the LAs with the best dynamic binding energy of -2112.06 kcal/mol was tightly bounded on the simulated DLC mechanical coated boundary inter-surface and was also found to be better than the commercial LAs, ZDDP in term of binding energy and onset temperature. This investigation will help in rational additive design and synthesis of new and better selective Las