Group member: Sthembiso Gumede

Sthembiso Gumede has been a member of the group for a number of years.  Currently he is well into his research for PhD on tethered membranes and their stability.  Previously, Sthembiso completed a MSc degree on polymer translocation, also in the group.

We appreciate funding of his work from the National Institute for Theoretical Physics.

Testing mathematics display on this site

Here is an equation based on integration over \(x\).  This is a test.

$$I_{\xi}=\int_{0}^{+\infty}\mathrm{d}x\,\,\left[\frac{\sin\left( x^2 \right)}{1+x^\pi} \right]$$

Janusz Meylahn MSc successful

Janusz Meylahn, group member and MSc student, has successfully passed his MSc exam.

We congratulate Janusz and wish him well in his next adventure!

Polymers and filaments in confined geometries

Imagine the filaments forming the cytoskeleton of a cell.  They are confined within the cell membrane.  Not only do these filaments influence how the cell might  behave mechanically, but how the filaments behave is coupled to the restricted space in which they grow, arrange or combine into networks.  Similarly one can think of polymers inside voids of another material, filling cracks or moving between the fillers in an elastomeric material.

For many years we have been interested in the how geometry and stiffness of polymer chains work together.  Mainly, this has been through the development of theoretical tools to describe such systems (see paper with Jerry Percus and Harry Frisch; there are others that will appear here shortly) but also recently through a string of simulations performed with Arash Azari at Stellenbosch University and the Centre for High Performance Computing in South Africa.

In a recent paper we investigated polymers of alternating stiffness all confined within a pore.  We observe how polymers become separated due to their stiffness.

Theoretical tools (using field-theoretical methods) allow careful analytical and perturbative ways to understand the role of networking, stiffness and inter- and intra-chain interactions.

Paper: Molecular dynamics simulations of polymer systems under geometrical confinement

Arash Azari, Kristian K. Müller-Nedebock “Entropic competition in polymeric systems under geometrical confinement”, EPL 110 68004 doi:10.1209/0295-5075/110/68004 (alternatively, http://arxiv.org/abs/1408.5312)

We present simulations of alternating copolymers of segments of different stiffness that are confined within regions.  Mixtures of different chains then have different arrangements depending on the size of the confining region.

In another paper we shall be addressing related (not identical) systems from a more analytical point of view.

Professor Sir Sam Edwards

In the daily scientific activities of this research group, the scientific insights and methods of Professor Sir Sam Edwards are very frequently employed.  We use his theoretical tools when studying networks or topology of polymers, and the understanding of the dynamics of polymers is forever influenced by his magnificent insights.

We remember a truly great physicist and remarkable and kind supervisor.

Professor Dame Athene Donald has written a lovely and comprehensive tribute to Sir Sam: On the loss of a giant.