Molecular Simulations of Surfactant Adsorption on Iron Oxide from Hydrocarbon Solvents was written by Acero, Pablo Navarro;Mohr, Stephan;Bernabei, Marco;Fernandez, Carlos;Dominguez, Beatriz;Ewen, James P.. And the article was included in Langmuir in 2021.Category: esters-buliding-blocks The following contents are mentioned in the article:
The performance of organic friction modifiers (OFMs) depends on their ability to adsorb onto surfaces and form protective monolayers. Understanding the relationship between OFM concentration in the base oil and the resulting surface coverage is important for improving lubricant formulations. Here, we use mol. dynamics (MD) simulations to study the adsorption of three OFMs: stearic acid (SA), glycerol monoostearate (GMS), and glycerol monooleate (GMO), onto a hematite surface from two hydrocarbon solvents: n-hexadecane and poly-伪-olefin (PAO). We calculate the potential of mean force of the adsorption process using the adaptive biasing force algorithm and the adsorption strength increases in the order: SA < GMS < GMO. We estimate the min. area occupied by OFM mols. on the surface using annealing MD simulations and obtained a similar hard-disk area for GMS and GMO, but a lower value for SA. Using the MD results, we determine the adsorption isotherms using the mol. thermodn. theory (MTT), which agree well with one previous exptl. data set for SA on hematite. For two other exptl. data sets for SA, lateral interactions between surfactant mols. need to be accounted for within the MTT framework. SA forms monolayers with lower surface coverage than GMO and GMS at low concentrations, but also has the highest plateau coverage. We validate the adsorption energies from the MD simulations using high frequency reciprocating rig friction experiments with different concentrations of the OFMs in PAO. For OFMs with saturated tailgroups (SA and GMS), we obtain good agreement between the simulations and the experiments The results deviate for OFMs containing Z-unsaturated tailgroups (GMO), due to the addnl. steric hindrance, which is not accounted for in the current simualtion framework. This study demonstrates that MD simulations, alongside MTT, are an accurate and efficient tool to predict adsorption isotherms at solid-liquid interfaces. This study involved multiple reactions and reactants, such as Glyceryl monostearate (cas: 31566-31-1Category: esters-buliding-blocks).
Glyceryl monostearate (cas: 31566-31-1) belongs to esters. Carboxylic acid esters of low molecular weight are colourless, volatile liquids with pleasant odours, slightly soluble in water. Many esters have the potential for conformational isomerism, but they tend to adopt an s-cis (or Z) conformation rather than the s-trans (or E) alternative, due to a combination of hyperconjugation and dipole minimization effects. The preference for the Z conformation is influenced by the nature of the substituents and solvent, if present. Lactones with small rings are restricted to the s-trans (i.e. E) conformation due to their cyclic structure.Category: esters-buliding-blocks
Referemce:
Ester – Wikipedia,
Ester – an overview | ScienceDirect Topics