The adsorption of mixed surfactants at the hydrophilic silica surface fromaqueous solution: Studied by specular neutron reflection

Specular neutron reflection has been used to determine the structure and co mposition of the mixed ionic non-ionic surfactants adsorbed ar the hydrophi lic silica solid/water interface. Measurements on two different mixed surfa ctant systems are reported: the cationic/nonionic mixture of hexadecyltrime thyl ammonium bromide, C(16)TAB, and hexaethylene glycol monododecyl ether, C12E6, and the anionic/nonionic mixture of sodium dodecyl sulfate, and C12 E6. For the C(16)TAB-C12E6 mixture, pH is shown to have a dramatic effect o n the relative affinity for adsorption of the two surfactants at the interf ace.