Molecular Dynamics Simulations of Langmuir-Blodgett Monolayers with Explicit Head-group Interactions

Packing of Simulated Friction Modifier Additives under Confinement

“…30,31 In addition, surfactant and Langmuir-Blodgett monolayers have been simulated on solid surfaces. [32][33][34][35][36][37][38][39][40][41][42][43][44] An interpretation tool used in some of these works is the density profile: the height-dependent local concentration of atoms between surfaces. In numerous simulations of systems such as united-atom spheres [45][46][47][48][49][50] or chains, [51][52][53][54][55][56][57][58][59] discrete layering has been calculated near flat or featured surfaces, with a tendency to reach the bulk concentration (and thus random intermolecular packing) after three layers.…”

Adsorption of Amino Acids and Glutamic Acid-Based Surfactants on Imogolite Clays

“…Elemental analysis results indicate that a significant amount of carbon is detected in the case of IMO–Glu, corresponding to 11.6 wt % of Glu adsorbed onto IMO (Supporting Information). Taking into account the specific surface area of the clays and by assuming that the outer surface (i.e., the Al-based surface) is entirely available for the physisorption, we could then estimate an effective headgroup area of 0.33 nm 2 (details of the calculation are reported in the Supporting Information), a value which is ∼1.5 times larger than what is found in tightly packed self-assembled monolayers formed by surfactants based on a carboxyl headgroup . Even more interesting is the comparison with the headgroup area at the air–water interface found in Glu-derived surfactants (0.88 nm 2 ) .…”

“…This value was calculated by taking into account the specific surface area of IMO resulting from porosimetry (317 ± 7 m 2 /g) and considering a value of 0.2 nm 2 for the area occupied by the polar head of the amino acid. 34 Water was then added to reach a total volume of 5 mL; the final concentration of amino acid was 4 mM, while the final concentration of IMO was 0.8 g/L. A 0.8 g/L dispersion of IMO without amino acid was prepared and then used as a reference for the adsorption experiments.…”

“…Taking into account the specific surface area of the clays and by assuming that the outer surface (i.e., the Albased surface) is entirely available for the physisorption, we could then estimate an effective headgroup area of 0.33 nm 2 (details of the calculation are reported in the Supporting Information), a value which is ∼1.5 times larger than what is found in tightly packed self-assembled monolayers formed by surfactants based on a carboxyl headgroup. 34 Even more interesting is the comparison with the headgroup area at the air−water interface found in Glu-derived surfactants (0.88 nm 2 ). 52 These findings suggest a quite dense packing of Glu molecules onto the outer IMO surface, paving the way toward the use of glutamic acid as a building block in the design and fabrication of hybrid materials based on imogolites.…”

“…The amount was chosen to theoretically cover twice the surface area of the IMO in the sample. This value was calculated by taking into account the specific surface area of IMO resulting from porosimetry (317 ± 7 m 2 /g) and considering a value of 0.2 nm 2 for the area occupied by the polar head of the amino acid . Water was then added to reach a total volume of 5 mL; the final concentration of amino acid was 4 mM, while the final concentration of IMO was 0.8 g/L.…”