Interfacial energies of clean mica and of monomolecular films of fatty acids deposited on mica, in aqueous and non-aqueous media

Bailey, A.I.; Price, Andrea G.; Kay, Susan M.

doi:10.1039/sd9700100118

Cited by 16 publications

(4 citation statements)

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“…The interfacial energy of freshly cleaved mica in water is 107 mJ m −2 ; addition of an amphiphilic surfactant (lauryl acid) that coats the mica surface reduces it to 8 mJ m −2 . 27 A coacervate consisting of two polar polyelectrolytes - HA and fp-151-RGD - effectively decreases interfacial energy to <1 mJ m −2 . The low interfacial energy of coacervates (~0.1 mJ m −2 ) has recently been confirmed by another group using atomic force microscopy.…”

Section: Resultsmentioning

confidence: 99%

Viscosity and interfacial properties in a mussel-inspired adhesive coacervate

et al. 2010

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The chemistry of mussel adhesion has commanded the focus of much recent research activity on wet adhesion. By comparison, the equally critical adhesive processing by marine organisms has been little examined. Using a mussel-inspired coacervate formed by mixing a recombinant mussel adhesive protein (fp-151-RGD) with hyaluronic acid (HA), we have examined the nanostructure, viscosity, friction, and interfacial energy of fluid-fluid phase-separated coacervates using the surface forces apparatus and microscopic techniques. At mixing ratios of fp-151-RGD:HA resulting in marginal coacervation, the coacervates showed shear-thickening viscosity and no structure by cryo-transmission electron microscopy (cryo-TEM). However, at the mixing ratio producing maximum coacervation, the coacervate showed shear-thinning viscosity and a transition to a bicontinuous phase by cryo-TEM. The shear-thinning viscosity, high friction coefficient (>1.2), and low interfacial energy (<1 mJ m−2) observed at the optimal mixing ratio for coacervation are promising delivery, spreading and adhesion properties for future wet adhesive and coating technologies.

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Section: Resultsmentioning

confidence: 99%

Viscosity and interfacial properties in a mussel-inspired adhesive coacervate

et al. 2010

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“…Measuring the γ associated with capillary/meniscus forces has garnered significant attention using the SFA and AFM and through theoretical models. ,,− Once a capillary bridge between two surfaces is formed, as in the case of the experiments performed in this article, the surfaces are held together by the meniscus forces generated in the bridge. This adhesion corresponds to the γ of the aqueous/coacervate phase interface and is directly connected to the capillary pressure difference (Δ P ) across this interface, as defined by the Young–Laplace equation. normalΔ P = γ ( 1 r 1 + 1 r 2 ) …”

Section: Resultsmentioning

confidence: 99%

Interfacial Energy of Polypeptide Complex Coacervates Measured via Capillary Adhesion

2012

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A systematic study of the interfacial energy (γ) of polypeptide complex coacervates in aqueous solution was performed using a surface forces apparatus (SFA). Poly(L-lysine hydrochloride) (PLys) and poly(L-glutamic acid sodium salt) (PGA) were investigated as a model pair of oppositely charged weak polyelectrolytes. These two synthetic polypeptides of natural amino acids have identical backbones and differ only in their charged side groups. All experiments were conducted using equal chain lengths of PLys and PGA in order to isolate and highlight effects of the interactions of the charged groups during complexation. Complex coacervates resulted from mixing very dilute aqueous salt solutions of PLys and PGA. Two phases in equilibrium evolved under the conditions used: a dense polymer-rich coacervate phase and a dilute polymer-deficient aqueous phase. Capillary adhesion, associated with a coacervate meniscus bridge between two mica surfaces, was measured upon the separation of the two surfaces. This adhesion enabled the determination of the γ at the aqueous/coacervate phase interface. Important experimental factors affecting these measurements were varied and are discussed, including the compression force (1.3-35.9 mN/m) and separation speed (2.4-33.2 nm/s). Physical parameters of the system, such as the salt concentration (100-600 mM) and polypeptide chain length (N = 30, 200, and 400) were also studied. The γ of these polypeptide coacervates was separately found to decrease with both increasing salt concentration and decreasing polypeptide chain length. In most of the above cases, γ measurements were found to be very low, <1 mJ/m(2). Biocompatible complex coacervates with low γ have a strong potential for applications in surface coatings, adhesives, and the encapsulation of a wide range of materials.

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“…Freshly cleaved mica is one of the most suitable substrates for wetting experiments because the resulting surface is hard, homogeneous, impermeable, and atomically flat. As the surface energy of mica of about 300 mJ/m 2 (in air) is much higher than the surface tensions of hexane (18.6 mN/m) and the dendrimer (29.3 mN/m), it satisfies the macroscopic condition for spreading ( S > 0). However, this did not occur, as is shown in Figure a, where one can see droplets on top of a thin layer adsorbed directly on the substrate.…”

Section: Resultsmentioning

confidence: 99%

Contact Angle Microscopy on a Carbosilane Dendrimer with Hydroxyl End Groups: Method for Mesoscopic Characterization of the Surface Structure

et al. 1997

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A carbosilane dendrimer containing hydroxyl terminal groups, which showed two types of wetting in dependence of the substrate used, was studied by tapping force microscopy. Due to the preferential adsorption of the hydroxyl groups, the dendrimer displayed autophobic spreading on mica, whereas a substrate which was first coated with a semifluorinated polymer was only partially wetted. In both cases, submicrometer-sized droplets were deposited on the surface. Microscopic contact angles were measured and compared with macroscopic values obtained by a standard sessile drop technique. The comparison showed lower values for the microscopic angle which were explained by deformation of the droplets caused by the tapping tip. The oscillatory motions of the tip intermittently touching a viscoelastic sample were calculated using a simple model of the tapping mode. The indentation of the tip into the sample and the induced phase shift relative to the oscillations in air were determined from the model, showing a good agreement with experimental results. Compared to traditional methods, this approach offers advantages such as (i) three-dimensional visualization of the whole droplet, (ii) submicrometer resolution of the structure near the three-phase boundary, and (iii) accurate determination of small contact angles.

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Interfacial energies of clean mica and of monomolecular films of fatty acids deposited on mica, in aqueous and non-aqueous media

Cited by 16 publications

References 0 publications

Viscosity and interfacial properties in a mussel-inspired adhesive coacervate

Viscosity and interfacial properties in a mussel-inspired adhesive coacervate

Interfacial Energy of Polypeptide Complex Coacervates Measured via Capillary Adhesion

Contact Angle Microscopy on a Carbosilane Dendrimer with Hydroxyl End Groups: Method for Mesoscopic Characterization of the Surface Structure

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