Theoretical and computational soft matter

The theoretical activity in the Soft Matter group is led by Dr James Adams, Dr Dave Faux and Dr Richard Sear. We undertake theoretical and computational research on soft matter, and collaborate with experimentalists both within our group and internationally. Our activity spans both pure and applied research, and soft materials ranging from polymer networks to cements.

James Adams' research focuses on constitutive properties of soft solids and complex fluids. Research into complex fluids such as polymer solutions and wormlike micellar solutions focuses on understanding their constitutive relation. This is important in applications ranging from injection molding of plastics to drilling oil wells. Research into soft solids has focussed on the novel properties of liquid crystal elastomers, including the unusual anisotropic mechanical behaviour of smectic phases and their ferroelectric response, and the role of hairpin defects in the mechanical properties of main chain systems. Their unusual mechanical response may lead to applications in strain sensing, or as switchable adhesives.

Dave Faux's research includes studies of the molecular dynamics of diffusion and surface adsorption in nanoporous systems (often models of cements), as well as work at larger length scales which uses Lattice Boltzmann and Monte Carlo simulations of transport in complex geometries. A second and equally important strand of the theoretical work focuses on proper interpretation of NMR relaxation times of fluids in porous media with a view to learning both about the confining microstructure (pore size distribution; pore connectivity) and of the fluids within (surface wetting; surface adsorption; inter-pore exchange rates etc).

Richard Sear's research is mostly on crystallisation, but also includes other areas of soft matter physics. He also collaborates on quantitative experiments on crystal nucleation. The focus of the crystallisation research is the fundamentals of how crystals nucleate and grow. Systems of interest range from ice to small molecules (eg glycine) in solution, to membrane proteins, as well as simple model systems such as the Gaussian Core Model and Lennard-Jones model potential. Typical techniques are computer simulation to look at the microscopic mechanism of nucleation, and statistical models to model quantitatively the experimental phenomenology of crystallisation. His research also includes modelling 'paint drying', i.e., the non-equilibrium physics of self-organisation in a colloidal suspension where the liquid is evaporating.This is in conjunction with the group's Joe Keddie.

A computer simulation snapshot of a state between a liquid and a crystal

All the atoms shown are the same type (Gaussian Core Model), different colours are used to indicate different local environments of a molecule. Yellow molecules are in a locally face centred cubic environment, orange are hexagonal close packed, green are body-centred cubic, purple are mostly at crystal/crystal interfaces, and blue are liquid-like. The state shown has almost all the molecules in locally crystalline environments but scatter X-rays like a liquid.

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Computer simulation snapshot of a state between a liquid and a crystal

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Dr Richard Sear
Soft Matter Group Leader, Department of Physics
University of Surrey