Molecular Dynamics Computational Study of Sustainable Green Surfactant for Application in Chemical Enhanced Oil Recovery.

Green surfactant (GS) flooding, an environmentally friendly chemical Enhanced Oil Recovery (cEOR) method, is explored in this molecular dynamics (MD) simulation study. This study evaluates the ability of (S)-2-dodecanamido-aminobutanedioic as a GS for cEOR, assessing its performance with hexane (C6), dodecane (C12), and eicosane (C20) as representative oils. In the case of the bulk system, a comprehensive molecular-level investigation provides structural details such as the radial distribution function, solvent-accessible surface area, GS adsorption dynamics, diffusivity, and emulsion stability of the GS, oil, and water systems. Also the impact of the three distinct oils on interfacial tension was examined in the existence of GS molecules. The findings reveal rapid GS molecule aggregation and adsorption on oil droplets, with various impacts on emulsion stability depending on the oil type. Additionally, GS enhances the aggregation of heavy C20 oil molecules in a water medium. The study demonstrates GS's role as an effective emulsifier, facilitating oil droplet recovery, with electrostatic interactions governing micelle formation and van der Waals interactions influencing oil droplet emulsification. These results align with prior experimental data, affirming GS's promising application potential in cEOR while prioritizing environmental sustainability.

Molecular dynamic simulations of self-assembly of amphiphilic comb-like anionic polybenzoxazines.

Fully atomistic molecular dynamic simulations were performed to address the self-assembly of amphiphilic and comb-like polybenzoxazines (iBnXz) in water, with i = 3 (trimer), i = 4 (tetramer); i = 6 (hexamer), i = 8 (octamer), and i = 10 (decamer). Spontaneous aggregation of these comb-like polybenzoxazine molecules into a single micelle occurs in the simulations. The simulations show that molecular size and concentration play important roles in micellar morphology. At an iBnXz concentration of 50 mM, the 3BnXz and 4BnXz molecules aggregate into spherical micelles, whereas the 6BnXz, 8BnXz, and 10BnXz molecules aggregate into cylindrical micelles. The micellar morphology is spherical at low concentrations, but undergoes a transition to cylindrical shape as concentration increases. The transition point depends on the molecular size-both the true size as indicated by molecular weight, as well as an additional effective size dependent on molecular flexibility.

Synthesis and evaluation of novel anionic polymeric surfactants based on polybenzoxazines.

A novel platform of anionic polymeric surfactants, poly(4HBA-oca(-)Na(+)), poly(4HBA-dea(-)Na(+)), and poly(4HBA-doa(-)Na(+)), has been synthesized by polymerizing benzoxazine monomers that are synthesized by reacting an aliphatic amine of variable chain length (C8, C10 and C12), with 4-hydroxybenzoic acid and paraformaldehyde. The structures of the monomers and polymeric surfactants are confirmed by NMR and FTIR. The ring-opening polymerization and thermal behavior of the benzoxazine monomers are studied by DSC and TGA. Size exclusion chromatography (SEC) coupled with Viscotek triple detection technique is used to characterize the molecular weight distribution of polybenzoxazine surfactants. The surfactants have low MW, varying from 2200 to 6000, and are fairly polydisperse. The influence of the structure on the surface activity is investigated by measuring the surface tension of aqueous solutions of the polymeric surfactants using the Wilhelmy plate method. The tensiometry results indicate that the adsorption at the air/water interface is similar for the octylamine, decylamine and dodecylamine-based surfactants. Increasing the alkyl chain length from C8 to C12 does not significantly affect the surface tension at the critical micelle concentration (γcmc), while the critical micelle concentration (cmc) gradually increases due to increasing hydrophobic effect. These polymeric surfactants give cmc values ranging from 0.12 g/L to 0.17 g/L, comparable to other polymeric surfactants reported in the literature. The influences of salt addition on the surface tension at the critical micelle concentration (γcmc) for these surfactants are studied. Theminimum values of the γcmc are observed around 1 wt% NaCl for the polybenzoxazine surfactant solution.