We explore colloidal materials - with a specific focus on surfactants, self assembly and carbon nanomaterials. We use a range of techniques to explore these materials, from atomic force microscopy and colour interferometry to small-angle neutron and X-ray scattering. Below you can find information on some of the systems and phenomena that we research.
Responsive stabilisers and self-assembly
Most colloidal systems in real applications contain one or more stabilisers in the form of surface active small molecules (surfactants), polymers and particles. By incorporating chemical functionality into these species that allows their properties to be changed by some stimulus, systems with enhanced capabilities can be developed. These might include drug carriers that can release their payload on command, precious catalysts that can be captured after use, and systems for capturing pollutants.
A stimulus to effect a chemical change can be internal (such as a change in pH, ionic strength, temperature, etc.) or from external sources such as light, electrical or magnetic fields. Of these, light is particularly appealing as it is a simple, clean and low-energy method to affect such changes. Many chemicals experience a reaction to light of certain wavelengths, taking the form of either a chemical reaction (photochemistry) or a change in shape (photoisomerisation). Our primary interest lies with the latter class, and in particular the azobenzene family of chemicals.
Complex colloidal forces
Colloidal systems such as emulsions, foams and particle dispersions continually experience dynamic forces in the form of brownian motion and gravity. These, and ever-present surface forces may encourage flocculation, phase separation or coalescence. Particularly in emulsions and foams, the interplay of surface forces, hydrodynamics during collisions and deformations of bubbles and droplets forms a complex picture. Deconvoluting this requires carefully chosen experiments and rigorous theoretical modelling.
We are especially interested in complex, multi-component systems, where more exotic colloidal forces can occur. These include polymer bridging interactions, depletion interactions and structural interactions. Such forces are highly dependent on the type and concentration of additives, offering new pathways for functional complex fluids.
Small-angle scattering of soft systems
Self-assembly, whereby molecules orient and arrange themselves into organised structures, is a crucial mechanism in many biological processes. We seek to learn from biology, and devise systems in which strutures can be obtained that provide desirable properties for templating, drug delivery and development of complex materials. Such self-assembled structures include micelles, liquid crystals and microemulsions, all of which have characteristic internal length scales on the order of nanometres.
Small-angle neutron and X-ray scattering (SANS and SAXS) are tools used to analyse the structure and interactions within such nano-structured soft matter systems. Specifically, the concept of contrast in SANS, whereby we make use of the strong difference in scattering between hydrogen and deuterium allows us to selectively highlight specific structures and interfaces within samples. We run SANS and SAXS experiments at neutron and X-ray sources around the world, including the Australian Synchrotron (Melbourne, Australia), ISIS (Didcot, near Oxford, UK), the Institut Laue-Langevin (Grenoble, France) and the Bragg Institute (Lucas Heights, near Sydney, Australia).
Smart materials and coatings from carbon nanostructures
The most appealing materials for the next generation of smart materials and coatings are those that incorporate multiple functionalities while remaining biodegradable and preferably bio-resourcable. Carbon nanomaterials are particularly appealing due to their remarkable mechanical, chemical and electronic properties. We are particularly interested in investigating the colloidal properties of these materials, to better understand how self- and directed-assembly can be used to make functional products.
We work closely with the Australian Pulp and Paper Institute seeking novel applications of cellulosic materials in self-assembled coatings, as well as groups in Materials Science and Aerospace Engineerings.