The structure of mixed nonionic surfactant monolayers at the air–water interface: the effects of different alkyl chain lengths

2003 ◽  
Vol 262 (1) ◽  
pp. 235-242 ◽  
Author(s):  
J Penfold ◽  
E Staples ◽  
I Tucker ◽  
R.K Thomas ◽  
R Woodling ◽  
...  
Keyword(s):  
Nonionic Surfactant ◽  
Alkyl Chain ◽  
Water Interface ◽  
Surfactant Monolayers ◽  
Air Water Interface ◽  
Chain Lengths

The Determination of the Structure and Coverage of Nonionic Surfactant Monolayers at the Air-Water Interface Using Neutron Reflection Technique

1994 ◽  
Vol 376 ◽  
Author(s):  
Jian R. Lu ◽  
Robert K. Thomas
Keyword(s):  
Nonionic Surfactant ◽  
Gaussian Distribution ◽  
Water Interface ◽  
Surfactant Monolayers ◽  
Neutron Reflection ◽  
Air Water Interface ◽  
Oligoethylene Glycols

ABSTRACTThe coverage and structure of the monododecyl ethers of oligoethylene glycols, C12Em where m = 2, 4, 6 and 8, adsorbed at the air-water interface have been studied by neutron reflection. At their c.m.c.s, the area per molecule is 33 ± 3 Å2 for C12E2, 44 ± 3 Å2 for C12E4 55 ± 3 Å2 for C12E6 and 62 ± 3 Å2 for C12E8. In terms of the width of a Gaussian distribution at 1/e of its height the thicknesses of the dodecyl chains are found to be constant at 16 ± 2 Å and those of the heads to vary from 11 to 19±2Å from m = 2 to 8. There is also found to be some overlap between the two chains at the interface.

The influence of electrolytes on gaseous monolayers II. Ionized films

1955 ◽  
Vol 232 (1189) ◽  
pp. 159-172 ◽  
Keyword(s):  
Surface Potential ◽  
Quaternary Ammonium ◽  
Alkyl Chain ◽  
Electrolyte Concentration ◽  
Ammonium Ion ◽  
Water Interface ◽  
Ammonium Halides ◽  
Air Water Interface ◽  
Good Agreement ◽  
The Ideal

An equation of state for a charged monolayer spread on an aqueous solution of a 1:1 electrolyte at 20°C in the absence of cohesive interactions has been derived, namely II = 2 kT / A-A o + 6.10√ c cosh sinh -1 133/ A √ c 6.10√ c . It has been found to apply to soluble charged films at hydrocarbon/water interfaces. In the case of insoluble monolayers of both alkyl quaternary ammonium halides and sodium alkyl sulphates at the hydrocarbon/water interface there is evidence of considerable ( ~50 %) ion-pair association, and this appears to be even further enhanced at the air/water interface at least for sulphate films. Surface potentials, measured by both the radioactive electrode and vibrating plate condenser techniques have been found to be in good agreement. The surface potential of sulphate monolayers in contrast to the ideal behaviour of quaternary ammonium films has been found to be dependent not only on the electrolyte concentration and film area but also on the nature of the interface, the nature of the substrate and at the air/water interface on the chain length. This has been attributed to a reorientation of the film molecules at the interface. Differences in the surface potential behaviour of sulphate and quaternary ammonium films are explained by suggesting that whereas with the sulphate film restricted rotation about the C—O bond can lead to different configurations of the sulphate ion with respect to the alkyl chain, only one configuration is possible for the symmetrical quaternary ammonium ion. Surface potential evidence indicates that contrary to what has been suggested previously, sulphate monolayers are completely dissociated in the acid-base sense.

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