Tail Ordering Due to Headgroup Hydrogen Bonding Interactions in Surfactant Monolayers at the Water-Oil Interface
Interactions between surfactants, and the resultant ordering of surfactant assemblies, can be tuned by the appropriate choice of head- and tailgroups. Detailed studies of the ordering of monolayers of long-chain n-alkanoic and n-alkanol monolayers at the water-vapor interface have demonstrated that rigid-rod all-trans ordering of the tailgroups is maintained upon replacing the alcohol with a carboxylic acid headgroup. In contrast, at the water-hexane liquid-liquid interface, we demonstrate that substitution of the -CH{sub 2}OH with the -COOH headgroup produces a major conformational change of the tailgroup from disordered to ordered. This is demonstrated by the electron density profiles of triacontanol (CH{sub 3}(CH{sub 2}){sub 29}OH) and triacontanoic acid (CH{sub 3}(CH{sub 2}){sub 28}COOH) monolayers at the water-hexane interface, as determined by X-ray reflectivity measurements. Molecular dynamics simulations illustrate the presence of hydrogen bonding between the triacontanoic acid headgroups that is likely responsible for the tail ordering. A simple free energy illustrates the interplay between the attractive hydrogen bonding and the ordering of the tailgroup.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 914222
- Report Number(s):
- BNL-78790-2007-JA; JPCBFK; TRN: US200804%%599
- Journal Information:
- J. Phys. Chem. B, Vol. 110; ISSN 1089-5647
- Country of Publication:
- United States
- Language:
- English
Similar Records
X-ray Scattering Studies of Long-Chain Alkanol Monolayers at the Water-Hexane Interface
Theoretical vibrational sum-frequency generation spectroscopy of water near lipid and surfactant monolayer interfaces