A comparison of didodecyldimethylammonium bromide adsorbed at mica/water and silica/water interfaces using neutron reflection.
The layer structure of the dichain alkyl ammonium surfactant, didodecyldimethylammonium bromide (DDAB), adsorbed from water on to silica and mica surfaces has been determined using neutron reflection. Although sometimes considered interchangeable surfaces for study, we present evidence of significant differences in the adsorbed layer structure below the critical micelle concentration. A complete DDAB bilayer was assembled at the water/mica interface at concentrations below the critical micelle concentration (CMC). In contrast it is not until the CMC was reached that the complete bilayer structure formed on the oxidised silicon crystal. Removal of the complete bilayer on both surfaces was attempted by both washing and ion exchange yet the adsorbed structure proved tenacious.
BP Institute and Department of Chemistry, University of Cambridge, Madingley Road, Cambridge, Cambs CB3 0EZ, UK.
Lucy R
LR
Griffin
BP Institute and Department of Chemistry, University of Cambridge, Madingley Road, Cambridge, Cambs CB3 0EZ, UK.
Kathryn L
KL
Browning
BP Institute and Department of Chemistry, University of Cambridge, Madingley Road, Cambridge, Cambs CB3 0EZ, UK.
Chris L
CL
Truscott
ISIS, Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK.
Luke A
LA
Clifton
ISIS, Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK.
John
J
Webster
BP Institute and Department of Chemistry, University of Cambridge, Madingley Road, Cambridge, Cambs CB3 0EZ, UK. Electronic address: stuart@bpi.cam.ac.uk.
Stuart M
SM
Clarke
Adsorption; DDAB; Didodecyldimethylammonium bromide; Mica; Neutron reflection; Silica; Surfactant