Role of viscoelastic interfaces in emulsion rheology and drop deformation

Abstract

The small-deformation behavior of single Newtonian oil drops covered by an adsorbed viscoelastic protein layer and suspended in a Newtonian protein-free matrix phase was investigated in simple shear flow. A simple but effective technique is presented to coat the drops with a layer of surface-active protein (lysozyme), which was adsorbed irreversibly to the oil/water interface. The adsorption and network formation at the interface are tracked by interfacial shear and dilatational rheometry using a biconical disk interfacial rheometer and pendant drop tensiometry. While the clean drop is deforming to the expected ellipsoidal shape in shear flow according to the Taylor theory, the protein-covered drop is able to resist the bulk shear stress to a much higher degree. We propose that this effect is due to the adsorbed protein, which is known to form strong, gel-like viscoelastic networks when adsorbed at oil/water interfaces.

Keywords

interfacial gels / globular proteins / interfacial rheology / drop deformation / emulsions

References

[1] EdwardsD. A., BrennerH., WasanD. T.Interfacial transport processes and rheology [M], 1991, Stonheam MA, Butterworth-Heinemann

[2] FullerG. G.BendingD. M., WaltersK.. Rheology of mobile intefaces [C]. Rheology Reviews [M], 2003, Aberystwyth, The British Society of Rheology: 77-124

[3] PalierneJ. P.. Linear rheology of emulsions with interfacial tension [J]. Rheologica Acta, 1990, 29: 204-214

[4] van HemelrijckE., van PuyveldeP., VelankarS., et al.. Interfacial elasticity and coalescence suppression in compatibilized polymer blends [J]. Journal of Rheology, 2004, 48: 143-158

[5] JacobsU., FahrlanderM., WinterhalterJ., et al.. Analysis of palierne’s emulsion model in the case of viscoelastic interfacial properties [J]. Journal of Rheology, 1999, 43: 1495-1509

[6] OldroydJ. G.. The effect of interfacial stabilizing films on the elastic and viscous properties of emulsions [C]. Proceedings of the Royal Society of London A, 1955, 232: 567-577

[7] WilliamsA., JanssenJ. J., PrinsA.. Behaviour of droplets in simple shear flow in the presence of a protein emulsifier [J]. Colloids and Surfaces A, 1997, 125: 189-200

[8] TaylorG. I.. The formation of emulsions in definable fields of flow [C]. Proceedings of the Royal Society of London A, 1934, 146: 501-523

[9] StoneH. A.. Dynamics of drop deformation and breakup in viscous fluids [J]. Annual Review of Fluid Mechanics, 1994, 26: 65-102

[10] FlumerfeltR. W.. Effects of dynamic interfacial properties on drop deformation and orientation in shear and extensional flow fields [J]. Journal of Colloid and Interface Science, 1980, 76: 330-349

[11] PhillipsW. J., GravesR. W., FlumerfeltR. W.. Experimental studies of drop dynamics in shear fields-role of dynamic interfacial effects [J]. Journal of Colloid and Interface Science, 1980, 76: 350-370

[12] Barthes-BieselD., DiazA., DheninE.. Effect of constitutive laws for two-dimensional membranes on flow-induced capsule deformation [J]. Journal of Fluid Mechanics, 2002, 460: 211-222

[13] ChangK. S., OlbrichtW. J.. Experimental studies of the deformation and breakup of a synthetic capsule in steady and unsteady simple shear-flow [J]. Journal of Fluid Mechanics, 1993, 250: 609-633

[14] Barthes-BieselD., SgaierH.. Role of membrane viscosity on the orientation and deformation of a spherical capsule suspended in shear flow [J]. Journal of Fluid Mechanics, 1985, 160: 119-135

[15] ErniP., FischerP., WindhabE. J., et al.. Stress- and strain-controlled measurements of interfacial shear viscosity and viscoelasticity at liquid/liquid and gas/liquid interfaces [J]. Review of Scientific Instruments, 2003, 74: 4916-4924

[16] OhS. G., SlatteryJ. C.. Disk and biconical interfacial rheometers [J]. Journal of Colloid and Interface Science, 1978, 67: 516-525

[17] ScrivenL. E.. Dynamics of a fluid interface: Equation of motion for newtonian surface fluids [J]. Chemical Engineering Science, 1960, 12: 98-108

[18] GundeR., KumarA., Lehnert-BatarS., et al.. Measurement of the surface and interfacial tension from maximum volume of a pendant drop [J]. Journal of Colloid and Interface Science, 2001, 244: 113-122

[19] FreerE. M., YimK. S., FullerG. G., et al.. Interfacial rheology of globular and flexible proteins at the hexadecane/water interface: Comparison of shear and dilatational deformation [J]. Journal of Physical Chemistry B, 2004, 108: 3835-3844