From aggregative adsorption to surface depletion: aqueous systems of C_nE_m amphiphiles at hydrophilic surfaces

TY - JOUR

T1 - From aggregative adsorption to surface depletion

T2 - aqueous systems of CnEm amphiphiles at hydrophilic surfaces

AU - Rother, Gernot

AU - Müter, Dirk

AU - Bock, Henry

AU - Schoen, Martin

AU - Findenegg, Gerhard H.

PY - 2017/6/18

Y1 - 2017/6/18

N2 - Adsorption of a short-chain nonionic amphiphile (C6E3) at the surface of mesoporous silica glass (CPG) was studied by a combination of adsorption measurements and mesoscale simulations. Adsorption measurements covering a wide composition range of the C6E3 + water system show that no adsorption occurs up to the critical micelle concentration, at which a sharp increase of adsorption is observed that is attributed to ad-micelle formation at the pore walls. Intriguingly, as the concentration is increased further, the surface excess of the amphiphile begins to decrease and eventually becomes negative, which corresponds to preferential adsorption of water rather than amphiphile at high amphiphile concentrations. The existence of such a surface-azeotropic point has not previously been reported in the surfactant adsorption field. Dissipative particle dynamics simulations were performed to reveal the structural origin of this transition from aggregative adsorption to surface depletion. The simulations indicate that this transition can be attributed to the repulsive interaction between head groups, causing depletion of the amphiphile in the region around the corona of the surface micelles.

AB - Adsorption of a short-chain nonionic amphiphile (C6E3) at the surface of mesoporous silica glass (CPG) was studied by a combination of adsorption measurements and mesoscale simulations. Adsorption measurements covering a wide composition range of the C6E3 + water system show that no adsorption occurs up to the critical micelle concentration, at which a sharp increase of adsorption is observed that is attributed to ad-micelle formation at the pore walls. Intriguingly, as the concentration is increased further, the surface excess of the amphiphile begins to decrease and eventually becomes negative, which corresponds to preferential adsorption of water rather than amphiphile at high amphiphile concentrations. The existence of such a surface-azeotropic point has not previously been reported in the surfactant adsorption field. Dissipative particle dynamics simulations were performed to reveal the structural origin of this transition from aggregative adsorption to surface depletion. The simulations indicate that this transition can be attributed to the repulsive interaction between head groups, causing depletion of the amphiphile in the region around the corona of the surface micelles.

KW - Adsorption

KW - mesoscale simulations

KW - nanopores

KW - surface azeotrope

KW - surfactant

U2 - 10.1080/00268976.2017.1299234

DO - 10.1080/00268976.2017.1299234

M3 - Journal article

AN - SCOPUS:85016093193

SN - 0026-8976

VL - 115

SP - 1408

EP - 1416

JO - Molecular Physics

JF - Molecular Physics

IS - 9-12

ER -