Poly(dimethylsiloxane) molecular layers at the surface of water and of aqueous surfactant solutions

Mann, Elizabeth K.; Langévin, D.

doi:10.1021/la00054a016

Cited by 60 publications

(72 citation statements)

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“…For the liquid phase, the elasticity has been directly measured: K g =40 mN/m. 9 The liquid phase can certainly be considered incompressible. The case of the polymer gas is uncertain, since experimental data give only an upper limit for its elasticity, still well above the K g ϳ / L transition between the two regimes.…”

Section: A Basic Approximationsmentioning

confidence: 99%

“…The case of the polymer gas is uncertain, since experimental data give only an upper limit for its elasticity, still well above the K g ϳ / L transition between the two regimes. For PDMS, direct measurements of the elasticity of the gas phase cannot distinguish it from nothing at all, 9 but this limit is only ϳmN/ m, so we turn to surface pressure measurements for a more accurate limit. The surface pressure at gas-liquid coexistence is itself immeasurably low ͑⌸Ͻ0.02 mN/ m͒.…”

Section: A Basic Approximationsmentioning

confidence: 99%

“…9,10 The polymer, poly͑dimeth-ylsiloxane͒ or PDMS, has served as a model polymer for many experimental studies on wetting for example. It is unusually flexible, with a particularly low surface viscosity.…”

Section: Introductionmentioning

confidence: 99%

“…It is unusually flexible, with a particularly low surface viscosity. On the water surface, it forms a monolayer one monomer ͑ϳ0.7 nm͒ thick, 9,11,12 so that the number of molecules in a full monolayer is inversely proportional to the number of monomer units in an average polymer chain. With less than full coverage by this monolayer, the polymer phase separates into a dense two-dimensional ͑2D͒ liquid phase and a very dilute 2D gas ͑see Fig.…”

Section: Introductionmentioning

confidence: 99%

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Hole dynamics in polymer Langmuir films

et al. 2006

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This article develops a model for the closing of a gaseous hole in a liquid domain within a two-dimensional fluid layer coupled to a Stokesian subfluid substrate, and compares this model to experiments following hole dynamics in a polymer Langmuir monolayer. Closure of such a hole in a fluid layer is driven by the line tension at the hole boundary and the difference in surface pressure within the hole and far outside it. The observed rate of hole closing is close to that predicted by our model using estimates of the line tension obtained by other means, assuming that the surface pressure in the gas is negligible. This result both supports the model and suggests an independent means of determining the line tension. Unlike most previous hydrodynamics models of Langmuir films, the closing of a hole necessarily involves vertical motion of the underlying incompressible fluid. Fluid is dragged along with the liquid monolayer towards the center of the hole, and must plunge away from the surface. An explicit expression is found for this vertical fluid flow in the bulk substrate.

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Section: A Basic Approximationsmentioning

confidence: 99%

Section: A Basic Approximationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hole dynamics in polymer Langmuir films

et al. 2006

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“…PDMS alone at the air-water interface forms a fairly dense, compact film with chains essentially parallel to the surface and little looping into the bulk [8]. One can imagine several possibilities for the mixed film: one of the components may be excluded from the interfacial region, leaving a pure film; surfactant and polymer may mix to form a homogeneous film; polymer and surfactant may segregate into patches to form a hetero geneous film; or polymer and surfactant may segregate vertically, forming nearly separate layers at the interface.…”

Section: Polydimethylsiloxane-surfactant Mixed Monolayersmentioning

confidence: 99%

Polymer-Surfactant Mono and Bilayers

Langévin

1997

Rev. Inst. Fr. Pét.

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Malgré de nombreux travaux sur les associations entre polymères et tensioactifs en solution, les associations localisées sur des sur faces ont été beaucoup moins étudiées. Dans cette présentation différents exemples seront présentés: des polymères non solubles dans l'eau étalés à la surface de solutions aqueuses de tensioac tifs, des polymères hydrosolubles adsorbés avec des molécules de tensioactifs à la surface de la solution. La première situation sera illustrée par du PDMS (polydiméthylsiloxane) étalé sur des monocouches de tensioactifs de différentes longueurs de chaînes. La pénétration des chaînes de polymères dans la couche de tensioactifs a été étudiée à l'aide de différentes techniques (tension superficielle, ellipsométrie, réflecti vité de neutrons). Des exemples de la deuxième situation seront donnés à l'aide de deux polyélectrolytes (polystyrène sulfonate PSS and poly acrylamide sulfonate PAMPS) et différents tensioactifs (ioniques et non-ioniques). Les mesures de tension superficielles de solutions diluées de tensioactif non ionique (C10E6) montrent qu'il existe une forte interaction avec le PSS et pas d'interaction avec le PAMPS. Cet effet est probablement dû au caractère hydrophobe plus impor tant du squelette de la chaîne de PSS. Des expériences de dif fraction des rayons X et de microscopie électronique sur des phases lamellaires en présence de PSS montrent que les chaînes de polymères sont imbriquées à l'intérieur de la bicouche de ten sioactifs. Les interactions entre PSS et PAMPS avec des tensioac tifs cationiques (DTAB) de charges opposées ont aussi été étudiées par tension superficielle, ellipsométrie et appareil de force de film mince. Un complexe de surface étendu polymère/tensioactif se forme et un phénomène de stratification est observé dans les films minces formés à partir des solutions.(1) Avenue Albert Schweitzer, 33600 Pessac -France POLYMER-SURFACTANT MONO AND BILAYERSAlthough there are many studies of association of polymers and surfactants in solution, much less is known about their association at surfaces. In this paper, several examples will be presented: water insoluble polymers spread at the surface of surfactant aque ous solutions, water soluble polymers adsorbed with the surfactant at the surface of the solution.Examples of the first case will be given with PDMS (polydimethylsiloxane) spread onto monolayers of surfactants of differ ent chain lengths. The penetration of the polymer into the surfac tant layer has been studied with different techniques (surface tension, ellipsometry, neutron reflectivity). Examples of the second case will be given with two different poly electrolytes (polystyrene sulfonate PSS and polyacrylamide sul fonate PAMPS) and various surfactants (ionic and nonionic). REVUE DE L'INSTITUT FRANÇAIS DU PÉTROLE VOL. 52, N° 2, MARS-AVRIL 1997 109 POLYMER-SURFACTANT MONO AND BILAYERSSurface tension measurements of the dilute solutions with a non ionic surfactant (C10E5) show that there is a strong interaction with PSS and no interaction with PAMPS. This is pr...

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Mixed polymer‐surfactant layers at the air‐water interface

Mann

Langévin

Hénon

et al. 1994

Ber Bunsenges Phys Chem

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We have studied mixed molecular layers of polydimethylsiloxane (PDMS) and surfactants, using different techniques: surface tension, ellipsometry, neutron reflectivity and Brewster angle microscopy. On pure water, the polymer layer is generally inhomogeneous, showing surface domains of different discrete thicknesses. The penetration of the polymer into the surfactant monolayer found on the surface of aqueous surfactant solutions depends on the surfactant. On a surfactant layer with little penetration by the polymer, the polymer layer remained inhomogeneous. With other surfactants, the polymer penetrated appreciably into the surfactant layer, and the polymer layer was homogeneous. These differences between surfactants correlate with the wetting behavior of PDMS on the aqueous surfactant solutions.In this short review, we will summarize our recent findings on the wetting of PDMS on liquid substrates. Further details can be found in Refs. 2 -4 and 7 -8. Polydimethyl siloxane is a water insoluble polymer, with monomers [I]:The polymer chain is very flexible, with a persistence length of only a few angstroems, and even for high molecular weights, the polymer is liquid. The oxygen atoms of the silicon backbone give an amphiphilic character to the polymer, facilitating it to spread on water. Provided that the molecular weight M , is not too small (> 10000 in our studies), all the observations described show little dependence on M,. The spreading behaviour is unusual: minor quantities, corresponding to polymer film thicknesses below about 5 A spread extremely rapidly. The polymer unfolds to a flat configuration, with the oxygen close to water, and the methyl groups in contact with air [2]. Below this "monolayer coverage", the polymer forms islands at the water surface as evidenced with Brewster angle microscopy ( Fig. 1) [3]; the surface tension is indistinguishable from that of water or in other words, the surface pressure of the polymer is very low (Fig. 2). Above monolayer coverage which corresponds to a polymer surface concentration c, of about 0.75 mg/m2, the surface pressure increases abruptly, and saturates to a constant value near 9 mM/m. Up to this point, the behavior observed is common to many other water insoluble polymers, for which the surface pressure saturation indicates a collapse of the chains in three dimensions. For PDMS, the situation is more complex, as demonstrated by ellipsometric [4] and neutron reflectivity experiments [5] : the polymer film thickness increases by steps, Fig. 1 Brewster angle image of a large PDMS domain on water below monolayer coverage ( c < c , ) . The bright region is an (almost) polymer free region, its brightness is due to surface roughness. The dark region is dense in polymer (the polymer layer contribution to the reflectivity is comparable and opposite in sign to the roughness contribution).

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Poly(dimethylsiloxane) molecular layers at the surface of water and of aqueous surfactant solutions

Cited by 60 publications

References 2 publications

Hole dynamics in polymer Langmuir films

Hole dynamics in polymer Langmuir films

Polymer-Surfactant Mono and Bilayers

Mixed polymer‐surfactant layers at the air‐water interface

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