Atomic force microscopy images of lyotropic lamellar phases

Garza, Cristina; Thieghi, Leila Thomazelli; Castillo, Rolando

doi:10.1063/1.2483389

Cited by 10 publications

(6 citation statements)

References 14 publications

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“…It is known that dichain-branched AOT at higher concentrations forms a lamella. 29,30 The X-ray diffraction data of lyotropic liquid crystalline state of AOT−water (from 10 to 70% of AOT) have been reported by Fontell, 29 and according to experimental data, the area per molecule is ∼65 Å 2 (∼50 wt %) and the fundamental repeat distance is estimated to be ∼39−40 Å. Similar results were obtained by Garza et al 30 by using the atomic force microscope technique, observing a lamellar interlayer spacing of 40.4 ± 0.3 Å for the AOT (51.57 wt %)/water system.…”

Section: ■ Introductionmentioning

confidence: 99%

AOT Bilayer Adsorption on Gold Surfaces: A Molecular Dynamics Study

et al. 2019

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A molecular dynamics study was done to reveal the adsorption properties of sodium dioctyl sulfosuccinate (AOT) bilayers on gold Au(111) surfaces. Examining the rotational mobility of AOT molecules, we track that the correlation time of AOT molecules on the adsorbed layer is much higher. The data estimating the diffusive motion of AOT molecule show a substantially lower rate of diffusion (∼10 −10 cm 2 /s) in the adsorbed layers in comparison to other ones. The results show that an adsorbed layer is more rigid, whereas the outer layers undergo considerable lateral and vertical fluctuations.

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Section: ■ Introductionmentioning

confidence: 99%

AOT Bilayer Adsorption on Gold Surfaces: A Molecular Dynamics Study

et al. 2019

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“…This suggests some further rearrangement after drying, from which the surfactant is then unable to reorganise into a hydrophilic coating when the contact angle experiment is repeated after rinsing. C 12 E 5 has previously been shown to form lamellar structures at high concentrations in water [ 44 ]. Whilst the substrate on which these structures form is significantly different, with a liquid interface compared to a polymer, it is possible that a similar structure forms at the surface of the polymer, minimising contact of hydrophilic head groups with a low surface energy polymer, and simultaneously presenting a low surface energy interface to the air.…”

Section: Discussionmentioning

confidence: 99%

Water-Resistant Surface Modification of Hydrophobic Polymers with Water-Soluble Surfactant Additives

et al. 2021

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Water-soluble nonionic surfactant, pentaethylene glycol monododecyl ether, C12E5, spontaneously blooms to the surface of spin-cast hydrophobic polyisoprenes, generating hydrophilic surfaces. This system provides a simple model for hydrophilic chemical modification of rubbery polymers that demonstrates surprisingly rich, complex, and unexpected behaviour. The vertical depth profiles were quantified using neutron reflectometry (NR) using a novel procedure to account for undulations in the film thickness. Surface properties were characterized using contact angle analysis and atomic force microscopy (AFM). Despite the low surface tension of the toluene solvent used in film preparation and the low surface energy of the polyisoprene (PI) matrix, NR depth profiles revealed clear evidence of surfactant segregation. This surface layer was typically thicker than a monolayer, but incomplete, yet was remarkably stable with respect to dissolution, even when exposed to hundreds of thousands of times the volume of water required to dissolve all the surfactant on the surface. Despite the apparent resistance to removal from the surface, water exposure does alter the subsequent wettability of the surface, with a hydrophilic-to-hydrophobic transition occurring after rinsing. Complementary AFM images of these C12E5/cis-PI films showed unexpected strand-like features on the surface of the film, which we attribute to a non-uniform lateral distribution of some of the surfactant. This surface structure becomes more evident after rinsing, and it appears that there are two distinct populations of surfactant on the PI film surface. We conclude that some of the bloomed surfactant exists as layers, which are relatively inert with respect to rinsing or surface modification, and some is laterally inhomogeneous. This latter population is primarily responsible for surface wetting behaviour but is not detected by specular NR.

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“…This suggests some further rearrangement after drying, from which the surfactant is then unable to reorganise into a hydrophilic coating when the contact angle experiment is repeated after rinsing. C12E5 has previously been shown to form lamellar structures at high concentrations in water [52]. Whilst the substrate on which these structures form is significantly different, with a liquid interface compared to a polymer, it is possible that a similar structure forms at the surface of the polymer, minimising contact of hydrophilic head groups with a low surface energy polymer, whilst also presenting a low surface energy interface to the air.…”

Section: Surface Structuresmentioning

confidence: 99%

Water-Resistant Surface Modification of Hydrophobic Polymers With Water-Soluble Surfactant Additives

Gibson¹,

Litwinowicz²,

Tellam³

et al. 2021

Preprint

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Water-soluble nonionic surfactant, pentaethylene glycol monododecyl ether, C12E5, spontaneously blooms to the surface of spin-cast hydrophobic polyiso-prenes, generating hydrophilic surfaces. This system represents a simple model for hydrophilic chemical modification of rubbery polymers yet demonstrates surprisingly rich, complex and unexpected behaviour. The ver-tical depth profiles were quantified using neutron reflectometry (NR) and deuterated surfactant, and the surface properties were characterized using con-tact angle analysis and atomic force microscopy (AFM). Despite the low surface tension of the toluene solvent used in film preparation and the low surface en-ergy of the PI matrix, NR depth profiles revealed clear evidence of surfactant segregation. This surface layer was typically thicker than a monolayer, but incomplete, yet was remarkably stable with respect to dissolution, even when exposed to hundreds of thousands of times the volume of water required to dissolve all the surfactant on the surface. Despite the apparent resistance to removal from the surface, water exposure does alter the subsequent wettabil-ity of the surface, with a hydrophilic-to-hydrophobic transition occurring after rinsing. Complementary AFM images of these C12E5 / cis-PI films showed unexpected strand-like features on the surface of the film, which we attribute to a non-uniform lateral distribution of some of the surfactant. This surface structure becomes more evident after rinsing, and it appears that there are two distinct populations of surfactant on the PI film surface. We conclude that some of the bloomed surfactant exists as layers, which are relatively inert with respect to rinsing or surface modification, and some is laterally inhomogene-ous. This latter population is primarily responsible for surface wetting be-havior, but is not detected by specular NR.

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Atomic force microscopy images of lyotropic lamellar phases

Cited by 10 publications

References 14 publications

AOT Bilayer Adsorption on Gold Surfaces: A Molecular Dynamics Study

AOT Bilayer Adsorption on Gold Surfaces: A Molecular Dynamics Study

Water-Resistant Surface Modification of Hydrophobic Polymers with Water-Soluble Surfactant Additives

Water-Resistant Surface Modification of Hydrophobic Polymers With Water-Soluble Surfactant Additives

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