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The Miscibility of Sodium Dodecyl Sulfonate with Anionic, Nonionic and Cationic Surfactants in Mixed Monolayers and Micelles

Wydro P.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 12

2157-2169

EN

The surface properties of sodium dodecyl sulfonate (SDSn), dodecyl-b-D-glucoside (DG), dodecyltrihydroxyethylammonium bro mide (DTEAB) and sodium dodecyl sul fate (SDS) and their mixtures: SDSn/SDS, SDSn/DG and SDSn/DTEAB were studied. The miscibility and the composition of the mixed monolayers and micelles as well as the interactions between their components were analyzed with the Motomura theory. It was found that among the investigated mixed systems the best surface properties reveal the anionic-cationic mixtures. Moreover, the investigated systems mix nonideally both in the monolayers and micelles. The magnitude of the deviations from ideal behaviour increases in the order: an ionic/an ionic < an ionic/nonionic << an ionic/cationic. Both the mixed monolayers and mi celles formed from SDSn/SDS and SDSn/DG mix tures are richer, as compared to the mixed solutions, in the more surface-active component, while the mixed monolayers and micelles formed from cationic/anionic mixtures (SDSn/DTEAB) possess more symmetrical composition than the mixed solution. As it was found the interactions between molecules both in the mixed monolayers and micelles are more attractive or less repulsive as compared to those in respective one-component monolayers and micelles and the strength of these interactions increases in the order: SDSn/SDS < SDSn/DG < SDSn/DTEAB.

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Electrical Properties and Relaxation Behavior of TOPO Monolayers Formed at the Air/Water Interface

Wydro P., Hąc-Wydro K.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 1

115-127

EN

The properties of the Langmuir monolayer formed by tri-n-octylphosphine oxide (TOPO) have been analyzed. The investigations were based both on traditional (surface potential measurements) and more advanced (the relative reflectivity using Brewster angle microscopy BAM) experimental techniques and, for better analysis, the semiempirical computation using HyperChem programme has been done. Moreover, detailed characteristics of the relaxation behaviour of TOPO monolayers have been performed. It has been found that with the increase of the surface pressure () the film thickness increases, and TOPO monolayer becomes denser; however its state does not change. Upon film compression, the reorientation of TOPO molecules occurs in this way that they become progressively more perpendicular to the surface until the collapse of the monolayer. The relaxation of TOPO monolayers formed both on water subphase as well as on NaCl solution of various concentrations were analyzed according to two-steps desorption mechanism. As it turned out, the stability of TOPO monolayer decreases with the surface pressure. At lower the loss of the monolayer material is controlled both by dissolution and diffusion mechanism, while at higher surface pressure the monolayer relaxation is controlled by two dissolution steps of different rates and the monolayer does not achieve a steady-state. Moreover, the monolayer stability increases with ionic strength.

3

Insoluble Amphiphiles at the Air/Water Interface. The Characteristics of Alcohols Monolayers

Wydro P., Hąc-Wydro K., Paluch M.

Polish Journal of Chemistry

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2006

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Vol. 80, nr 12

2041-2054

EN

In this paper thorough characteristics of monolayers formed at the air/water interface by two alcohols namely hexadecanol and octadecanol has been presented. The experiments were based on surface pressure/area and surface potential measurements. The visualization of monolayers has been performed using Brewster Angle Microscopy. It has been found that both alcohols form at the air/water interface condensed monolayers with transition between liquid condensed (LC) and solid (S) state. From the experimental results the thickness of monolayers has been calculated and compared with theoretical value. These calculations allow drawing conclusion of the slope of the hydrocarbon tails of investigated alcohols in monolayers. From the surface potential measurements the conformation of the O–H bond and the orientation of dipolemoments of both alcohols have been proposed. Moreover, the stability of monolayers formed by investigated alcohols has been studied and it has been found lower stability of hexadecanol monolayers in comparison with those formed by octadecanol.

4

A Study of the Properties of Tri-n-octylphosphine Oxide (TOPO) Monolayers at the Air/Water Interface

Hąc-Wydro K., Wydro P., Dynarowicz-Łątka P.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 4

773-781

EN

Tri-n-octylphosphine oxide (TOPO) was found to be capable of Langmuir monolayer formation at the air/water interface. Surface pressure-area ( -A) isotherms obtained at different experimental conditions (barrier speed, number of deposited molecules, temperature and presence of metal ions in the aqueous subphase), compression modulus (Cs 1) values andBAMimages have been analyzed. The stability of TOPO monolayers has also been thoroughly examined. The obtained results indicate a liquid state of TOPO monolayers independently of subphase temperature or ionic strength. Such experimental conditions as the barrier speed or the number of deposited molecules were found to have no influence on the shape and position of the isotherms. Moreover, the performed experiments proved a high stability of monolayers from TOPO at the air/water interface.