Multilayering of Calcium Aerosol-OT at the Mica/Water Interface Studied with Neutron Reflection: Formation of a Condensed Lamellar Phase at the CMC

TY - JOUR

T1 - Multilayering of Calcium Aerosol-OT at the Mica/Water Interface Studied with Neutron Reflection

T2 - Formation of a Condensed Lamellar Phase at the CMC

AU - Griffin, L. R.

AU - Browning, K. L.

AU - Lee, S. Y.

AU - Skoda, M. W.A.

AU - Rogers, S.

AU - Clarke, S. M.

PY - 2016/12/13

Y1 - 2016/12/13

N2 - Using specular neutron reflection, the adsorption of sodium and calcium salts of the surfactant bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT or AOT) has been studied at the mica/water interface at concentrations between 0.1 and 2 CMC. The pH dependence of the adsorption was also probed. No evidence of the adsorption of Na(AOT) was found even at the critical micelle concentration (CMC) while the calcium salt was found to adsorb significantly at concentrations of 0.5 CMC and above. This interesting and somewhat unexpected finding demonstrates that counterion identity may be used to tune the adsorption of anionic surfactants on anionic surfaces. At the CMC, three condensed bilayers of Ca(AOT)2 were adsorbed at pH 7 and 9 and four bilayers adsorbed at pH 4. Multilayering at the CMC of Ca(AOT)2 on the mica surface is an unusual feature of this surfactant/surface combination. Only single bilayer adsorption has been observed at other surfaces at the CMC. We suggest this arises from the high charge density of mica which must provide an excellent template for the surfactant.

AB - Using specular neutron reflection, the adsorption of sodium and calcium salts of the surfactant bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT or AOT) has been studied at the mica/water interface at concentrations between 0.1 and 2 CMC. The pH dependence of the adsorption was also probed. No evidence of the adsorption of Na(AOT) was found even at the critical micelle concentration (CMC) while the calcium salt was found to adsorb significantly at concentrations of 0.5 CMC and above. This interesting and somewhat unexpected finding demonstrates that counterion identity may be used to tune the adsorption of anionic surfactants on anionic surfaces. At the CMC, three condensed bilayers of Ca(AOT)2 were adsorbed at pH 7 and 9 and four bilayers adsorbed at pH 4. Multilayering at the CMC of Ca(AOT)2 on the mica surface is an unusual feature of this surfactant/surface combination. Only single bilayer adsorption has been observed at other surfaces at the CMC. We suggest this arises from the high charge density of mica which must provide an excellent template for the surfactant.

UR - http://www.scopus.com/inward/record.url?scp=85005950948&partnerID=8YFLogxK

U2 - 10.1021/acs.langmuir.6b03601

DO - 10.1021/acs.langmuir.6b03601

M3 - Journal article

AN - SCOPUS:85005950948

SN - 0743-7463

VL - 32

SP - 13054

EP - 13064

JO - Langmuir

JF - Langmuir

IS - 49

ER -