Jeroen van Duijneveldt's research group

Soft condensed matter

The term soft condensed matter refers to a range of systems that fall between simple liquids and solids, for instance colloidal suspensions, emulsions, liquid crystals, and polymers. This includes many systems of practical or biological importance, such as inks, paints, shampoos, foodstuffs, milk and blood. Real systems tend to be complex, consisting of many components that are often difficult to characterise in detail. Well-defined model systems are therefore studied instead. A central theme is the use of polymers to control particle interactions, structure and phase behaviour in colloidal suspensions.

Please contact me if you are interested in studying for a Ph.D. in any of the areas listed

Cluster phase in contact-lens shaped particles Entropy driven cluster phase

For particles with hard interactions (closely approximated by colloids with steeply repulsive interactions), the internal energy does not depend on particle positions and any phase transitions are driven by an increase of entropy. Thin discs can form a liquid crystalline (nematic) phase, but when curvature is introduced the nematic phase is frustrated and a transition to a locally ordered cluster phase is found. More commonly cluster phases arise from a competition between particle attractions and repulsions, but here the process is driven purely by geometric constraints.

Nematic liquid crystal formed in a suspension of modified sepiolite clay Colloidal liquid crystals

Particles that are sufficiently non-spherical (either rod-like or plate-like) can form liquid crystalline phases, in particular a nematic phase, on increasing concentration. For the first time, we have succeeded in obtaining such ordered suspensions starting from a natural clay, sepiolite. A pronounced fractionation with respect to rod length is found, with the long rods accumulating in the nematic phase.

Colloid - polymer mixture in the protein limit Attraction through repulsion

Presence of non-adsorbing polymer in solution induces a depletion attraction between suspended particles. This can lead to phase separation, aggregation or gelation. This mechanism is relevant to practical formulations and addition of polymer allows a fine control of particle attractions. The mechanism also applies in the so-called protein limit, where the polymer chains are much larger than the suspended (nano-)particles. Addition of polymers is useful to help proteins crystallise. Recently we demonstrated phase separation and gelation induced by adding crosslinked polymer (microgel) particles.

Particle mixtures

Mixtures of repulsive colloidal particles of different shapes and sizes quite generally have a tendency to demix - with a variety of equilibrium and non-equilibrum structures resulting in practice.

Unbinding booksNematic phase of colloidal platelets

Polymers and surfactants are used to prepare non-aqueous suspensions of clay platelets, in which the original clay stacks are fully exfoliated into single sheets. High aspect ratio platelets can be obtained this way. Small-angle X-ray scattering is a powerful technique to study these systems at the nanometre length scale and is done in collaboration with Prof. Robert Richardson.

SAXS from liquid crystal suspension Liquid crystals as structured solvents

Liquid crystal suspensions consist of a (thermotropic) liquid crystal used as solvent for colloidal particles. In the nematic phase the presence of the colloidal particles (spheres, rods, platelets) introduces defects in the liquid crystalline host material which leads to novel particle interactions. The X-ray scattering pattern on the left is from a clay suspension in 5CB. The nematic liquid crystal is aligned in a magnetic field and gives rise to a diffuse scattering peak. The bright scattering peaks are due to the suspended clay platelets and demonstrate that the platelets here are aligned perpendicular to the liquid crystal director.

Smectic-A phaseModels for (colloidal) liquid crystals

Molecules or particles that are strongly non-spherical, that is either rod-like or disc-like, tend to form liquid crystalline phases that display a degree of order in between an isotropic liquid and a crystal. We use Monte Carlo computer simulations to study how properties of the molecules, such as their shape, flexibility and the presence of polar groups influences the structure of the liquid crystalline phases and the phase behaviour.

Methods

Projects in our group usually involve the preparation of model systems, such as colloidal spheres or platelets of well-defined size. A variety of characterisation techniques are used, particularly scattering methods (light, X-rays, neutrons) and microscopy. Experimental work is complemented by computer simulations. Much of the work is collaborative and funding comes from a range of sources including industry.

PeopleGroup photo Feb 2015

PhD students Visitor

Past group members

Postdoctoral fellows PhD students

Funding

We acknowledge financial support from the University of Bristol, the Engineering and Physical Sciences Research Council (EPSRC), the European Union, the Nuffield Foundation, the Department for Education and Skills (DfES), the Mexican and Thai governments, Shell, Unilever, Hewlett-Packard, Bayer Cropscience, ICI / AkzoNobel, Imerys and Merck as well as beamtime allocations at Daresbury, ESRF, ILL and ISIS.

Curriculum vitae

Jeroen van Duijneveldt was appointed to a lectureship at the University of Bristol in 1997 and currently is reader in physical chemistry. He obtained his Ph.D. in 1994 at the Van 't Hoff Laboratory in Utrecht under supervision of Professor Henk Lekkerkerker and Dr. Jan Dhont. Subsequently, he joined the group of Professor Mike Allen at the Physics Department at the University of Bristol. His publications are listed here. He is a fellow of the the Royal Society of Chemistry (RSC; CChem FRSC), and member of the Royal Dutch Chemical Society, the Society of Chemical Industry and the Institute of Physics (CPhys MInstP). He is member of the colloid and surface chemistry group of SCI (operating jointly with the RSC Colloid and Interface Science Group) and past member and chairman of the RSC Bristol & District Section Committee.

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