molecular self-assembled materials
My interest is to understand the structure, properties and behaviour of soft materials formed by self-assembly of detergents, lipids and polymers into micelles, vesicles and liquid crystals. Although we focus on fundamental understanding, these compounds are found almost everywhere from pharmaceutical and industrial formulations to living systems. We examine these at the sub-nanometer to sub-micron scale by X-ray and neutron scattering at Australian and international facilities, as well as optical, electron and probe microscopy, calorimetry, and rheology. Each area is the basis for several possible Honours projects.
Project 1
Dynamics of amphiphilic polymer self-assembly or What is the difference between a micelle and a nanoparticle?
The classic cartoon picture of a surfactant micelle is a non-polar droplet coated by polar functional groups in contact with water. They look no different than a hydrophobic nanoparticle with hydrophilic surface groups. But this static picture hides the other main characteristic of micelles, and of all self-assembled structures. They exist in dynamic equilibrium. They exchange molecules with solvent, break up and reform, and also stretch, bend, vibrate, and rotate about their average shape. In contrast, a nanoparticle is static. We are exploring self-assembly between these two limiting cases using two novel kinds of polymeric amphiphiles1. Both allow us to vary the rate of each dynamic process in solution, and see changes in nanostructure when components are mixed or under flow. This can be used to control many important applications of amphiphiles including burst release rates in drug delivery systems, flow behaviour of personal care or industrial formulations, the rigidity of gels. or even the drying of paint.
Project 2
Chemical Exobiology: Self-assembly and self replication in ionic liquids
Water is basis of all life …on Earth. However, certain salts that are liquid at room temperature (ionic liquids) are also extraordinary solvents finding wide application in chemical synthesis. Some of them also support many of the necessary pre-conditions for life to emerge: They dissolve nonpolar solutes and salts, polymers, amino acids and polypeptides. Lipids and other amphiphiles self-assemble into bilayer membranes and other structures2. Could they be the basis of completely alien self-replicating precursors to forms of life in environments previously considered as just too hostile, too hot. or too "dry"?
Project 3
Surfactant-templated salts
Simple surfactants are widely used to template the formation of mesoporous silica for diverse applications including as adsorbents and catalysts. We have recently found that certain biogenic minerals like calcium carbonate and oxalate can also precipitate mesoporous solids, but seemingly only in a non-crystalline state analogous to glassy silica. The structures in these materials are much smaller than and quite different from natural biominerals. Here we seek to understand the formation and stability of these delicate inorganic nanostructures.
References
1 Ganeva, DE; Sprong, E; de Bruyn, H; Warr, GG; Such, CH and Hawkett, BS. Macromolecules, 40, 6181, 2007. DOI:10.1021/ma070442w; Chatjaroenporn, K; FitzGerald, PA; Baker, RW and Warr, GG. Langmuir, 26, 11715, 2010. DOI: 10.1021/la101159g
2 Hayes, R; Imberti, S; Warr, GG and Atkin, R. Phys. Chem. Chem. Phys., 13, 13544, 2011. DOI: 10.1039/c1cp21080g; Atkin, R; Bobillier, SMC and Warr, GG. J. Phys. Chem. B, 114, 1350-1360, 2010. DOI: 10.1021/jp910649a
For further information, please contact:
Room 310
School of Chemistry
Eastern Avenue
University of Sydney NSW 2006
Phone: +61 2 9351 2106
Email gregory.warr@sydney.edu.au
Website: http://sydney.edu.au/science/chemistry/~warr_g/