Surface Dilatational Modulus Research Articles

Effect of enzymatic hydrolysis on surface activity and surface rheology of type I collagen

We describe the adsorption behaviour and rheological properties of a calf skin type I collagen, and of its hydrolysates obtained using a Clostridium histolyticum collagenase (CHC) under moderate conditions (pH 7, 37°C). The effect of CHC concentration (2×10−9–2×10−6M) and incubation time (35–85min) was studied and optimised to achieve the highest decrease of surface tension and the highest dilational surface viscoelasticity of the adsorbed layers. SDS-PAGE electrophoresis and reverse-phase high performance liquid chromatography (RP-HPLC) were used to characterise the hydrolysis products. The results show that even simple modifications (heat treatment, pH change, partial hydrolysis) of collagen enhances its surface properties, especially in terms of surface dilational elasticity modulus. The use of low enzyme concentration (CHC-to-collagen molar ratio of 4×10−3) and short incubation time (<45min) results in moderately hydrolysed products with the highest ability to lower surface tension (γ=53.9mNm−1) forming highly elastic adsorbed layers (surface dilational elasticity, E′=74.5mNm−1).

Impact of the imaginary part of the surface dilatational modulus on the splashing behavior of drops.

The relation between the complex surface dilatational modulus E of aqueous surfactant solutions and the splashing behavior of their drops on liquid surfaces was investigated. The surface dilatational modulus E of selected surfactant systems has been determined in the frequency range of 3 to 500 Hz by means of the oscillating bubble technique. According to the functional dependence of the phase ϕ of the complex modulus E(ω, c)exp[iϕ(ω, c)] at higher frequencies, adsorption layers can be classified as surface elastic or surface viscoelastic. Each behavior shows pronounced differences in drop splashing experiments. The impact of a drop on the liquid was monitored with a high-speed camera. The splash of a drop is a rather complex phenomenon, so the focus of this article is to establish a relationship between the imaginary part of the surface dilatational modulus E and the height of the drop rebound. These findings may be of importance for formulations in crop protection, introducing a chemical way to influence the impact of drops on solid and liquid interfaces.

Understanding the role of monolayers in retarding evaporation from water storage bodies

Retardation of evaporation by monomolecular films by a ‘barrier model’ does not explain the effect of air velocity on relative evaporation rates in the presence and absence of such films. An alternative mechanism for retardation of evaporation attributes reduced evaporation to a reduction of surface roughness, which in turn increases the effective vapour pressure of water above the surface. Evaporation suppression effectiveness under field conditions should be predictable from measurements of the surface dilational modulus of monolayers and research directed to optimising this mechanism should be more fruitful than research aimed at optimising a monolayer to provide an impermeable barrier.

Changes in functionality of whey protein and micellar casein after high pressure – low temperature treatments

Changes in functional properties of micellar caseins (MC) and whey proteins (WPI) due to high pressure – low temperature (HPLT) treatments were investigated and compared to changes induced via high pressure treatments at room temperature (HP). Single whey protein solutions, micellar casein dispersions and two mixtures (micellar caseins:whey proteins weight mixing ratios 80:20 and 20:80) were treated at a concentration of 2% (w/w) and at two different pH values (7.0 and 5.8). Oscillating pendant drop and shear experiments were performed to identify changes in the rheological behavior at the air/water interface and in bulk, respectively. Foaming and emulsification experiments were conducted to investigate further impacts on the functional behavior. Both, HPLT and HP treatments led to a decreased emulsion stability for emulsions from WPI solutions independent from the treatment pH, while the foam stability was increased for these samples. In comparison, the changes for MC dispersions exhibited the same tendency but less pronounced. HPLT treatments of MC rich samples always led to the formation of a few very large flocs which had a major influence on the functional behavior. The rheological behavior of these samples changed from a Newtonian to a shear-thickening behavior. The elastic part of the surface dilatational modulus was increased for a pure WPI solution after HPLT and HP treatments while the viscous part remained unaffected. However, changes in functional properties highly depended on the sample composition and results for mixtures differ from those for pure dispersions.

Interfacial Properties of Fully Condensed Functional Silsesquioxane: A Langmuir Monolayer Study

We have studied interfacial properties of fully condensed octakis[{2-(3,4-epoxycyclohexyl)etyl}dimethylsilyloxy]octasilsesquioxane (OE-POSS). The surface pressure–area isotherm obtained in a Langmuir trough together with Brewster angle microscopy indicated formation of a stable, homogeneous liquid-like monolayer. For low molecular areas, the monolayer undergoes a stepwise collapse showing unusual multilayer morphology. A collapse mechanism is proposed to be a consequence of progressive decrease in the distance between silicon–oxygen cages after reorganization of side groups. Hysteresis experiment showed incomplete respreading of small aggregates and successive decrease in molecular areas. Relaxation measurements indicated a slight impact of desorption and molecular rearrangements on the monolayer stability. Interfacial rheology was investigated for compressional deformation of the air/water interface. Both components of surface dilational modulus (elastic, E′, and viscous, E″) were determined by the oscillating barriers method. With increasing frequency, E′ decreased while E″ increased almost linearly. The loss angle tangent indicated elastic response of the monolayer in the range of low deformation rates and viscous behavior when subjected to fast deformation. The rheological behavior of the monolayer is also strongly affected by the collapse mechanism that begins at 20 mN/m.

Dynamic adsorption and dilatational properties of BSA at oil/water interface: Role of conformational flexibility

The influence of protein concentration (c) and/or disulfide bond (S–S) cleavage with β-mercaptoethanol (2-ME) on interfacial adsorption dynamics, including diffusion, penetration and structural rearrangement at the interface, as well as dynamic dilatational properties of bovine serum albumin (BSA) was systematically investigated using drop shape analysis. The results indicated that for native BSA increasing the c from 0.01 to 0.5% (w/v) progressively improved the rate of diffusion and the ‘equilibrium’ surface pressure (π), while a further increase in c (to 1.0%, w/v) contrarily impaired these characteristics; increasing the c progressively improved the penetration and structural rearrangement at the interface. In contrast, the surface dilatational modulus (E) development was less dependent on the c than that for the π. On the other hand, the S–S cleavage with 2-ME at any test c value progressively improved the diffusion and penetration, as well as ‘equilibrium’ π, while the structural rearrangement was highly dependent on the c. At c < 0.5% (w/v), increasing the 2-ME concentration progressively improved the rearrangement, while at c values of 0.5% or above, a contrary trend was observed. The S–S cleavage generally improved the E or its elasticity development over the whole adsorption, regardless of the c. The E-π plots indicated that besides the adsorption, the lateral macromolecular interactions at the interface could be affected by variation in c and/or 2-ME concentration. The relationships between the conformational flexibility and interfacial characteristics of BSA, as well as between its interfacial and emulsifying properties have been well established.

Effect of sucrose ester concentration on the interfacial characteristics and physical properties of sodium caseinate-stabilized oil-in-water emulsions

The effect of sucrose ester (SE) concentration on interfacial tension and surface dilatational modulus of SE and sodium caseinate (NaCas)-SE solutions were investigated. The critical micelle concentration (CMC) of SE was presumed to be 0.05% by measuring interfacial tension of SE solution. The interfacial tension of NaCas-SE solution decreased with increased SE concentration. A sharp increase in surface dilatational modulus of NaCas solution was observed when 0.01% SE was added and a decline was occurred at higher SE level. The influence of SE concentration on droplet size and confocal micrograph, surface protein concentration, ζ-potential and rheological properties of oil-in-water (O/W) emulsions prepared with 1% NaCas was also examined. The results showed that addition of SE reduced droplet size and surface protein concentration of the O/W emulsions. The ζ-potential of the O/W emulsions increased initially and decreased afterward with increased SE concentration. All the O/W emulsions exhibited a shear-thinning behaviour and the data were well-fitted into the Herschel–Bulkley model.

Stiffness of Lipid Monolayers with Phase Coexistence

The surface dilational modulus--or compressibility modulus--has been previously studied for monolayers composed of pure materials, where a jump in this modulus was related with the onset of percolation as a result of the establishment of a connected structure at the molecular level. In this work, we focused on monolayers composed of two components of low lateral miscibility. Our aim was to investigate the compressibility of mixed monolayers at pressures and compositions in the two-phase region of the phase diagram, in order to analyze the effect of the mechanical properties of each phase on the stiffness of the composite. In nine different systems with distinct molecular dipoles and charges, the stiffness of each phase and the texture at the plane of the monolayer were studied. In this way, we were able to analyze the general compressibility of two-phase lipid monolayers, regardless of the properties of their constituent parts. The results are discussed in the light of the following two hypotheses: first, the stiffness of the composite could be dominated by the stiffness of each phase as a weighted sum according to the percentage of each phase area, regardless of the distribution of the phases in the plane of the monolayer. Alternatively, the stiffness of the composite could be dominated by the mechanical properties of the continuous phase. Our results were better explained by this latter proposal, as in all the analyzed mixtures it was found that the mechanical properties of the percolating phase were the determining factors. The value of the compression modulus was closer to the value of the connected phase than to that of the dispersed phase, indicating that the bidimensional composites displayed mechanical properties that were related to the properties of each phases in a rather complex manner.

Mixed soy globulins and β-lactoglobulin systems behaviour in aqueous solutions and at the air–water interface

It has been studied in this work the effect of mixing soy globulins (β-conglycinin and glycinin) with β-lactoglobulin (βlg) both in the bulk phase and also in their interfacial (air–water interface) and foaming properties, at pH 3.0 and 7.0 and 20 °C. The analyzed properties of these systems were: particle size distribution (by dynamic light scattering (DLS)); dynamics of adsorption and surface dilatational modulus (by tensiometry); foam formation and stability (by conductimetric and optical measurements). Results revealed that mixture of 7S soy globulin and βlg at pH 7.0 presented a synergistic effect that is reflected in the formation of interfacial films of enhanced elasticity. The foaming properties were also improved (better foam capacity with foams made up by smaller air bubbles). There exists a close relation between these results and that obtained by DLS (existence of a complexation between β-conglycinin and βlg).

Dynamics of complex fluid-fluid interfaces

EXTENDED ABSTRACT Surface rheological properties like surface shear viscosities, or surface dilatational moduli often play an important role in the stability and dynamic behavior of emulsions, foam, biological fluids, liquid jets, coatings flows, or immiscible polymer blends [1]. This is particularly true when the interfaces in these systems have a complex microstructure, for example, when the surface active components stabilizing the interface form a 2d gel phase, a 2d glass phase, or 2d (liquid) crystalline phase. Such 2d mesophases are typically formed when interfaces are stabilized by colloidal particles, proteins, protein aggregates, proteinpolymer complexes, or amphiphilic polymers [1]. Applied deformations induce changes in the microstructure of the interface, and the resulting changes in surface rheological properties (such as surface shear thinning, shear thickening, or thixotropic behavior) affect the behavior of the multiphase system on a macroscopic scale. Most currently available constitutive models for the surface extra stress tensor either do not account for the strain (rate) dependence of surface rheological properties, or are appropriate only for infinitesimally small rates, where departures from linear behavior are very small [1]. In this paper we will discuss recent advances in the development of nonlinear constitutive equations for the stress-deformation behavior of fluidfluid interfaces in the framework of nonequilibrium thermodynamics. We will focus on two frameworks: the classical irreversible thermodynamics (CIT) framework, and the general-equation-for-the-nonequilibrium-reversible-irreversiblecoupling (GENERIC) framework. We will illustrate the construction of surface rheological constitutive equations within these two frameworks for a specific example: interfaces stabilized by anisotropic colloidal particles, in the dilute particle concentration regime. In both frameworks we construct models describing the effect of microstructural changes on the nonlinear response of an interface to a deformation through a dependence of the surface stress tensor on a set of scalar and a tensorial structural variables. We present the time evolution equations for these structural variables, and evaluate the ability of these types of models to describe the shear thinning behavior typically observed experimentally for such interfaces. We compare the models in both simple and oscillatory shear. We find that both frameworks allow us to construct nonlinear expressions for the surface extra stress tensor capable of describing shear thinning behavior, but the CIT model gives realistic predictions only for small departures from equilibrium, whereas the GENERIC framework allows us to create models valid also far from equilibrium. Besides giving more accurate predictions for the shear thinning behavior the GENERIC model also predicts the existence of in-plane normal stresses (normal to the direction of flow), and effect of which its existence has been hypothesized, but that has so far not been observed experimentally. These results show that microstructural models developed using nonequilibrium thermodynamic frameworks provide a valuable tool for the analysis of the highly nonlinear dynamics of multiphase systems with complex liquid-liquid interfaces.

Surface Dilational Properties of Sodium 4-(1-methyl)-Alkyl Benzene Sulfonates: Effect of Alkyl Chain Length

AbstractThe dilational properties of absorbed film of three sodium 4-(1-methyl)-alkyl benzene sulfonates at the air-water interface have been investigated by drop shape analysis method. The influences of time, dilational frequency and surfactant bulk concentration on surface dilational modulus and phase angle have been expounded. The nature of interfacial film depends on the molecular structure of surfactants. For 2Φ-14 and 2Φ-16, the diffusion-exchange process controls the dilational properties and the film shows viscoelastic character. As an increase of the hydrophobic chain, the dilational modulus of 2Φ-18 is independent on applied frequency in the studied bulk concentration except for 1 × 105mol/L, which indicates the adsorbed layer behaves nearly purely elastic. Furthermore, the phase angle of 2Φ-14 and 2Φ-16 are remarkably higher than those of 2Φ-18, confirming that the presence of strong interactions between hydrophobic chains of 2Φ-18. Best agreements with the experimental data have been obtained from the curves of dilational modulusvs.surface pressure.

Surface rheological properties of liquid–liquid interfaces stabilized by protein fibrillar aggregates and protein–polysaccharide complexes

In this study we have investigated the surface rheological properties of oil–water interfaces stabilized by fibrils from lysozyme (long and semi-flexible and short and rigid ones), fibrils from ovalbumin (short and semi-flexible), lysozyme–pectin complexes, or ovalbumin–pectin complexes. We have compared these properties with those of interfaces stabilized by the native proteins. The surface dilatational and surface shear moduli were determined using an automated drop tensiometer and a stress controlled rheometer with biconical disk geometry. Results show that interfaces stabilized by complexes of these proteins with high-methoxyl pectin have higher surface shear and dilatational moduli than interfaces stabilized by the native proteins only. The interfaces stabilized by ovalbumin and lysozyme complexes have comparable shear and dilatational moduli though ovalbumin–pectin complexes are twice as large in radius as lysozyme–pectin complexes. Under most of the experimental conditions, interfaces stabilized by fibrils have the highest surface rheological moduli. The difference between long semi-flexible lysozyme fibrils or short rigid lysozyme fibrils is not pronounced in interfacial dilation rheology but significant in interfacial shear rheology. The complex surface shear moduli of interfaces stabilized by long semi-flexible fibrils are about 10 times higher than those of interfaces stabilized by short rigid fibrils, over a range of bulk concentrations. Interfaces stabilized by short and more flexible ovalbumin fibrils have a significantly higher surface shear modulus than those stabilized by longer and more rigid lysozyme fibrils. This study has shown that the use of such supra-molecular structural building blocks creates a wider range of microstructural features of the interface, with higher surface shear and dilatational moduli and a more complex dependence on strain.

The coupling between foam viscoelasticity and interfacial rheology

We study the impact of interfacial rheology on the linear viscoelastic relaxations of disordered 3D foams. Their complex shear modulus G* = G′ + iG′′ is measured as a function of frequency, bubble size, liquid viscosity and surface dilatational modulus. We show that for foams with very rigid interfaces the variations of G* with frequency f between 1 and 100 Hz deviate from the behavior previously predicted as a generic consequence of topological disorder and observed for foams with mobile or moderately rigid interfaces. Our experiments demonstrate that the relaxations slow down as the bubble size or the foaming liquid viscosity increases. We show under which conditions, depending on the interfacial rigidity, the loss factor G′′/G′ can be collapsed on master curves by applying a scale factor to the frequency. The dependence of this scale factor on the bubble size and viscosity constitutes a robust criterion helping to identify the dominant dissipation mechanism.

Surface and foam properties of SLES + CAPB + fatty acid mixtures: Effect of pH for C12–C16 acids

Recently we showed that triple surfactant mixtures, comprising the anionic surfactant SLES, zwitterionic surfactant CAPB and long-chain fatty acid (FAc), possess very high surface modulus which can be used to modify the dynamic properties of foams (Golemanov et al. Langmuir 2008, 24, 9956). In the current paper we perform a systematic experimental study of the effects of several factors on the surface tension, surface dilatational modulus, viscous friction inside sheared foam, foam-wall friction, and mean bubble size in sheared foams, for such triple surfactant mixtures. The factors studied are: (1) chain length of fatty acid; (2) fatty acid concentration; (3) pH; (4) presence of glycerol in the aqueous solution. Lauric (C12Ac), myristic (C14Ac) and palmitic (C16Ac) acids are studied. The concentrations of the main surfactants were fixed, 10mM for SLES and 5mM for CAPB. Varying the myristic acid (C14Ac) concentration, CC14Ac, we observed two ranges: (1) At CC14Ac<0.06mM, the acid increases the solution surface modulus up to 50mN/m, however, without affecting significantly any of the other properties studied; (2) At CC14Ac>0.11mM, C14Ac leads to significant decrease of surface tension (from 29 to 22mN/m), increase of surface modulus (from 50 to 400mN/m), decrease of mean bubble size in sheared foams (from 300 to 150μm), and strong increase of the inside-foam friction and foam-wall friction. Qualitatively similar results are obtained with the other FAc studied. Mass-balance estimates show that low surface tension and high surface modulus are observed, when the molar fraction of FAc in the adsorption layer approaches ca. 30%. The main role of FAc is to induce a surface phase transition, leading to formation of surface condensed phase in the mixed adsorption layer. For all systems studied, the increase of pH above a certain transitional value leads to a sharp increase of surface tension and decrease of surface dilatational modulus, which is accompanied with a decrease in the inside-foam and foam-wall viscous friction. The transitional pH value varies between 8 and 11, and increases with the fatty acid chain-length. The increase of pH causes ionization of the FAc molecules – the latter start to behave as usual anionic surfactant without forming surface condensed phase. The main effect of glycerol is to decrease the transitional pH (by 1 to 1.5 units for 40wt% glycerol), without affecting significantly the system properties away from the transitional pH. These results clarify the compositional domain, in which the fatty acids can be used for control of surface and foam properties in such surfactant mixtures.

Elastic Properties of Natural Sea Surface Films Incorporated with Solid Dust Particles: Model Baltic Sea Studies

Floating dust-originated solid particles at air-water interfaces will interact with one another and disturb the smoothness of such a composite surface affecting its dilational elasticity. To quantify the effect, surface pressure (Π) versus film area (A) isotherm, and stress-relaxation (Π-time) measurements were performed for monoparticulate layers of the model hydrophobic material (of μm-diameter and differentiated hydrophobicity corresponding to the water contact angles (CA) ranging from 60 to 140°) deposited at surfaces of surfactant-containing original seawater and were studied with a Langmuir trough system. The composite surface dilational modulus predicted from the theoretical approach, in which natural dust load signatures (particle number flux, daily deposition rate, and diameter spectra) originated from in situ field studies performed along Baltic Sea near-shore line stations, agreed well with the direct experimentally derived data. The presence of seawater surfactants affected wettability of the solid material which was evaluated with different CA techniques applicable to powdered samples. Surface energetics of the particle-subphase interactions was expressed in terms of the particle removal energy, contact cross-sectional areas, collapse energies, and so forth. The hydrophobic particles incorporation at a sea surface film structure increased the elasticity modulus by a factor K (1.29–1.58). The particle-covered seawater revealed a viscoelastic behavior with the characteristic relaxation times ranging from 2.6 to 68.5 sec.

A Surface Rheological Study of a Glucosamide-Based Trisiloxane Gemini Surfactant at the Air/Water Interface

The dilational viscoelastic properties of a glucosamide-based trisiloxane gemini surfactant at the air/water interface were investigated. Aqueous solutions of the glucosamide-based trisiloxane gemini surfactant were spread onto a pendant drop and the dynamic surface tensions were measured by means of axisymmetric drop shape analysis. The surface dilatational elasticity, viscosity, and phase angle of the adsorption monolayer were also determined by the oscillating drop technique. The influences of frequency and concentration on the surface dilational properties were expounded. It is showed that the surface dilational modulus and elastic modulus increased with the increase of frequency, the viscous modulus was complex, while the phase angle decreased with the increase of frequency. Surface dilational modulus, elastic modulus, and viscous modulus passed through the maximum with the increase of bulk concentration and the phase angle increased with the increase of concentration.

Surface dilational moduli of poly (ethylene oxide), poly (methyl methacrylate), and their blend films

Surface dilational moduli of poly (ethylene oxide) (PEO), poly (methyl methacrylate) (PMMA), and compatible PEO/PMMA blend films spread at the air–water interface were investigated as a function of surface concentration. The surface dilational modulus of an expanded PEO film increased as the surface concentration increased to 0.4mg/m2, which corresponds to the limiting surface area of PEO. After peaking at this value, the surface dilational modulus decreased with an increase in the PEO concentration. Lissajous orbits of PEO films exhibited positive hysteresis loops for all surface concentration ranges. On the other hand, the surface dilational modulus of a condensed PMMA film steeply increased as the surface concentration increased. Lissajous orbits of PMMA films changed from positive hysteresis loops to negative loops at the surface concentration at which the surface pressure reached in the plateau region. The magnitude of the surface dilational modulus of PMMA was larger than that of PEO at a fixed surface concentration. The surface dilational moduli of the PEO/PMMA blend films increased with the total surface concentration and their magnitudes were less than those of the individual PMMA films and larger than those of the individual PEO films at fixed surface concentrations. Lissajous orbits of the PEO/PMMA blend films also changed from positive hysteresis loops to negative loops beyond the surface concentration at which the plateau surface pressure of PEO was attained.

Interfacial Dynamics and Rheology of Polymer-Grafted Nanoparticles at Air–Water and Xylene–Water Interfaces

Particle-stabilized emulsions and foams offer a number of advantages over traditional surfactant-stabilized systems, most notably a greater stability against coalescence and coarsening. Nanoparticles are often less effective than micrometer-scale colloidal particles as stabilizers, but nanoparticles grafted with polymers can be particularly effective emulsifiers, stabilizing emulsions for long times at very low concentrations. In this work, we characterize the long-time and dynamic interfacial tension reduction by polymer-grafted nanoparticles adsorbing from suspension and the corresponding dilatational moduli for both xylene-water and air-water interfaces. The dilatational moduli at both types of interfaces are measured by a forced sinusoidal oscillation of the interface. Surface tension measurements at the air-water interface are interpreted with the aid of independent ellipsometry measurements of surface excess concentrations. The results suggest that the ability of polymer-grafted nanoparticles to produce significant surface and interfacial tension reductions and dilatational moduli at very low surface coverage is a key factor underlying their ability to stabilize Pickering emulsions at extremely low concentrations.

Adsorption and Dilatational Rheology of Heat-Treated Soy Protein at the Oil–Water Interface: Relationship to Structural Properties

We evaluated the influence of heat treatment on interfacial properties (adsorption at the oil-water interface and dilatational rheology of interfacial layers) of soy protein isolate. The related structural properties of protein affecting these interfacial behaviors, including protein unfolding and aggregation, surface hydrophobicity, and the state of sulfhydryl group, were also investigated. The structural and interfacial properties of soy protein depended strongly on heating temperature (90 and 120 °C). Heat treatment at 90 °C induced an increase in surface hydrophobicity due to partial unfolding of protein, accompanied by the formation of aggregates linked by disulfide bond, and lower surface pressure at long-term adsorption and similar dynamic interfacial rheology were observed as compared to native protein. Contrastingly, heat treatment at 120 °C led to a higher surface activity of the protein and rapid development of intermolecular interactions in the adsorbed layer, as evidenced by a faster increase of surface pressure and dilatational modulus. The interfacial behaviors of this heated protein may be mainly associated with more flexible conformation and high free sulfhydryl group, even if some exposed hydrophobic groups are involved in the formation of aggregates. These results would be useful to better understand the structure dependence of protein interfacial behaviors and to expand utilization of heat-treated protein in the formulation and production of emulsions.

A Surface Rheological Study of Silwet L-77 Surfactant at the Air/Water Interface

The dilational viscoelastic properties of Silwet L-77, a trisiloxane surfactant of the general formula (Me3SiO)2SiMe(CH2)3(OCH2CH2)7.5OH, at the air/water interface were investigated. Aqueous solutions of Silwet L-77 were spread onto a pendant drop and the dynamic surface tensions were measured by means of axisymmetric drop shape analysis. The surface dilatational elasticity, viscosity, and phase angle of the adsorption monolayer were also determined using the oscillating drop technique. The influences of frequency and concentration on the surface dilational properties were expounded. It is shown that the surface dilational modulus and elastic modulus increased with the increase of frequency, the viscous modulus was complex, while the phase angle decreased with the increase of frequency. Surface dilational modulus, elastic modulus, and viscous modulus passed through the maximum with the increase of bulk concentration and the phase angle increased with the increase of concentration.