The effect of hydroxyl on the solution behavior of a quaternary ammonium gemini surfactant

Abstract

The adsorption and viscoelastic properties of a micellar solution of 2-hydroxyl-propanediyl-1,3-bis(hexadecyldimethylammonium bromide), abbreviated as 16-3OH-16, have been investigated by surface tension and rheological measurements. Meanwhile, an aqueous solution of propanediyl-1,3-bis(hexadecyldimethylammonium bromide), abbreviated as 16-3-16, was also examined. From the steady state and oscillatory rheological results, a notable difference in shear viscosities between the two systems was observed. Zeta potentials and size distributions confirm the change in the potentials and hydrodynamic diameters, and these results are in good agreement with the rheological results. The differences of the two solutions were attributed to the effect of the hydroxyl group on the spacer of 16-3OH-16. Molecular dynamic simulations and density functional theory (DFT) calculations were performed to investigate the non-covalent interactions in the solution and the difference between the molecular orbitals and the electrostatic potentials. Our research shows that a more uniform distribution of positive charges around the spacer could result in a more effective electrostatic screening effect between the charged headgroups, and promote the formation of a worm-like micelle. Also, hyperconjugation becomes stronger when the hydroxyl group is introduced on the spacer of the gemini molecule.

Multispectroscopic and Computational Analysis Insight into the Interaction of Cationic Diester-Bonded Gemini Surfactants with Serine Protease α-Chymotrypsin

“…By obtaining the optimized structure and HOMO → LUMO, HOMO-1, and LUMO+1 for C m -E2O-C m and aromatic residues (Trp/Tyr) of α-CHT, it was observed that the LUMO energy of Trp and Tyr molecules is very high due to the electron-withdrawing carboxylate group (Figure ). The electronic cloud and LUMO energy of gemini surfactants and HOMO of Trp and Tyr residues are in agreement with MEP as the electrostatic interactions are also applicable between the cationic nitrogen portion of gemini surfactants and the aromatic residue of Trp/Tyr . Furthermore, on cautious perception of energy gap values of the concerned molecular orbitals, it is obvious that the concerned molecular orbitals have lower energy gap (Δ E ) values, recommending significant interactions between the frontier molecular orbitals (FMO); this perception is in incongruity with the postulate of FMO theory.…”

“…The electronic cloud and LUMO energy of gemini surfactants and HOMO of Trp and Tyr residues are in agreement with MEP as the electrostatic interactions are also applicable between the cationic nitrogen portion of gemini surfactants and the aromatic residue of Trp/Tyr. 57 Furthermore, on cautious perception of energy gap values of the concerned molecular orbitals, it is obvious that the concerned molecular orbitals have lower energy gap (ΔE) values, recommending significant interactions between the frontier molecular orbitals (FMO); 58 this perception is in incongruity with the postulate of FMO theory. According to FMO theory, interactions are conceivable only when the energy gap values are not extremely high between the molecular frontier orbitals.…”

The inactivation mechanism of chemical disinfection against SARS-CoV-2: from MD and DFT perspectives

“…[24][25][26] The approximate atomic charges are assigned by utilizing the Gasteriger method for the ethanol-/hypochlorite-3CL hydrolase systems, being used to evaluate electrostatic interactions. 27 For the silver ion-3CL hydrolase system, the charge of silver atom is set to 1.0e. The calculations of energy minimizations of all complex systems are conducted by adopting both the steepest descent and conjugate gradient algorithm at atmospheric pressure of 10 À4 GPa.…”

“…The system temperature is set as 300 K which is regulated by adopting the Berendsen thermostat. 27,28 All calculations at the density functional theory (DFT) level are conducted using DMol 3 package, as implemented in the Materials Studio. 29 The exchange-correlation interaction is described by the Perdew-Burke-Ernzerhof (PBE) functional within the generalized gradient approximation (GGA).…”

Micellization and Adsorption Properties of New Cationic Gemini Surfactants Having Hydroxyisopropyl Group

“…As dimensions of aggregates decrease with a temperature increase, the value of β diminishes as well. Though many researchers mentioned a decrease of aggregate dimensions when the temperature is elevated, a reason for this phenomenon was not explained. − …”