Filtyp
Water-in-oil-in-water double emulsions (W1/O/W2) consist of water droplets (W1) dispersed in oil globules (O), which are then redispersed in an external aqueous phase (W2). This paper reports multiple light scattering investigations on W1/O/W2 double emulsions, the inner W1/O emulsion being a concentrated micron sized inverse emulsion, and the outer O/W2 emulsion being a dense direct emulsion. Dou
We have investigated the structure of microgels formed during heating of demineralized β-lactoglobulin (βlg) solutions at pH 5.9 by small-angle X-ray scattering (SAXS) and light scattering. First, unheated βlg solutions were characterized at different pH values between 2.0 and 7.0. At pH 5.9, βlg solutions contain mainly dimers (with a radius of approx. 2nm), which coexist with a small number of l
We present a new 3D cross-correlation instrument that not only allows for static and dynamic scattering experiments with turbid samples but measures at four angles simultaneously. It thus extends the application of cross-correlation light scattering to time-resolved studies where we can, for example, efficiently investigate the temporal evolution of aggregating or phase separating turbid dispersio
Amphiphilic diblock copolymers such as poly(styrene)-block-poly(styrene sulfonate) (PS-b-PSS) (Matsuoka, H.; Maeda, S.; Kaewsaiha, P.; Matsumoto, K. Langmuir 2004, 20, 7412), belong to a class of new polymeric surfactants that ionize strongly in aqueous media. We investigated their self-assembly behavior in aqueous solutions and used them as an emulsifier to prepare electrosterically stabilized co
We studied the phase behavior of a model binary mixture of eye lens crystallin proteins using first-order thermodynamic perturbation theory. The instability boundary, or spinodal surface, was found to be very sensitive to the strength of the attraction between the two proteins, and also to respond to this interprotein attraction strength in a non-monotonic fashion. In particular, in the case of ei
We present a study of binary mixtures of eye lens crystallin proteins. A coarse-grained model of aqueous aand γ-crystallin mixtures based on molecular dynamics simulations and SANS experiments is proposed. Thermodynamic perturbation theory is implemented to obtain the stability boundaries, or spinodal surface, of the binary mixture in the full parameter space. The stability of these high-concentra
We determine the structure of charge-stabilized colloidal suspensions at low ionic strength over an extended range of particle volume fractions using a combination of light and small angle neutron scattering experiments. The variation of the structure factor with concentration is analyzed within a one-component model of a colloidal suspension. We show that the observed structural behavior correspo
We demonstrate how we can tune the size, shape, surface functionality and properties of nanoparticles and use them as ideal model systems for fundamental investigations as well as for materials applications. In particular we describe ways to create functionalized core-shell particles with various degree of anisotropy and interesting magnetic properties. We show how we can use these particles in or
We propose a minimal model for spherical proteins with aeolotopic pair interactions to describe the equilibrium phase behavior of lysozyme. The repulsive screened Coulomb interactions between the particles are taken into account assuming that the net charges are smeared out homogeneously over the spherical protein surfaces. We incorporate attractive surface patches, with the interactions between p
We have systematically investigated the phase diagram of clay particles in water to understand the relation between the local and macroscopic properties and the structures of clay suspensions. We focused, in particular, on sodium Cloisite (CNa) particles at concentrations typically used in nanocomposites (concentrations from 1 to 4 wt %) and at an extended range of ionic strengths (10-5 to 10-2 M
We present a combined experimental and numerical study of the equilibrium cluster formation in globular-protein solutions under no-added salt conditions. We show that a cluster phase emerges as a result of a competition between a long-range screened Coulomb repulsion and a short-range attraction. A simple effective potential, in which electrostatic repulsion is fixed by experimental conditions and
Small-angle neutron scattering experiments and molecular dynamics simulations combined with an application of concepts from soft matter physics to complex protein mixtures provide new insight into the stability of eye lens protein mixtures. Exploring this colloid-protein analogy we demonstrate that weak attractions between unlike proteins help to maintain lens transparency in an extremely sensitiv
We investigate the competition between spinodal decomposition and dynamical arrest using aqueous solutions of the globular protein lysozyme as a model system for colloids with short-range attractions. We show that quenches below a temperature Ta lead to gel formation as a result of a local arrest of the protein-dense phase during spinodal decomposition. The rheological properties of these gels all
We use small-angle scattering experiments to investigate the structural properties of aqueous lysozyme solutions under conditions where the existence of equilibrium clusters has recently been demonstrated (Nature 2004, 452, 492). We also discuss the possible emergence of a low angle scattering contribution, which recently attracted interest due to its appearance in solutions of various proteins. W
We report small-angle scattering experiments with two different types of model proteins, lysozyme and the eye lens protein γB-crystallin. We discuss the results in the context of recent suggestions that globular proteins possess a short-ranged attractive potential, and that simple models from colloid science could help to rationalize the best route for obtaining protein crystals and to interpret t
Colloidal liquids usually appear turbid due to the strong multiple scattering of electromagnetic waves from the particles in suspension. As the concentration increases, particle interactions induce positional correlations which generally lead to a reduced optical density (higher transparency). However, the optical properties of a colloidal liquid can be manipulated by tuning the interaction potent
Controlling interparticle interactions, aggregation and cluster formation is of central importance in a number of areas, ranging from cluster formation in various disease processes to protein crystallography and the production of photonic crystals. Recent developments in the description of the interaction of colloidal particles with short-range attractive potentials have led to interesting finding
We have studied various complex systems from particle and biopolymer gels to concentrated surfactant solutions using classical rheometry and optical microrheology. Optical microrheology uses dynamic light scattering, usually in the multiple scattering regime, to obtain information about the microscopic dynamic properties of complex media. This can be done either by direct investigation or by addit
