Polymers and complex fluids
PhD (ESR) positions are available within the "DYNACOP" Marie Curie Initial training network. (DYNamics of Architecturally COmplex Polymers). Two positions in Leeds, others at Universities across Europe. See here for more details.
PhD projects are available in all the areas below, and in more areas on the individual staff webpages. If you are interested, then please get in touch.
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Staff [ Oliver Harlen | Daniel Read ] Postdocs [ Ahamadi Malidi | Srinivas Yarlanki | Sathish Sukumaran | Kapileswar Nayak ] Students [ Samantha Harris | David Hoyle | Sung Ho Yoon ] 
Dr. Richard Blackwell Molecular Rheology of Branched Polymers and its Application to Wire Coating Dr. Richard Graham Molecular modelling of entangled polymer fluids under flow Dr. Sally Everitt Bubble dynamics in polymeric foams |
Polymer dynamics and rheology
Oliver Harlen, Daniel Read
Polymers are long molecules made from joining together lots of small
molecules (or monomers). Sometimes polymer molecules
are linear, but very often - notably in the case of Low Density
Polyethylene (LDPE) used to make plastic bottles -
they include many branches.During the manufacture of polymeric (or plastic) materials and commodities, liquids containing polymers are subjected to flow. The way these liquids react is determined by the shapes, or configurations that the molecules adopt. Polymer molecules behave like springs, and become stretched by the flow, giving rise to the strongly elastic behaviour of polymeric fluids. The study of the dynamics of polymer molecules is very important for the understanding of flow of polymeric fluids.
If polymer molecules overlap sufficiently, then they get tangled up (like spaghetti) so that they are constrained in their movement. The "tube model" for entangled polymers provides a conceptual framework for understanding the constrained motion, and for making mathematical predictions about the polymers' response to flow.
Branchpoints in the polymer molecules provide addtional obstacles to the motion of entangled polymers, so that the distribution of branchpoints in polymer molecules can be a critical factor in determining flow properties.
Non-Newtonian fluids
Oliver Harlen
Elastic stresses in polymeric and other complex fluids can give rise
to strange
flow behaviour not seen in Newtonian
fluids.
This can, for example, produce undesirable instabilities
in industrial processes. The aim of
our research
is to predict how these fluids will
flow
in various flow geometries and to determine
the conditions for the flow to become
unstable.
Our current research includes investigations
of how bubbles grow in polyurethane
foams;
how filaments of polymer stretch and
break-up;
and flow instabilities in extrusion.
Reaction chemistry and branched polymer architecture
Daniel Read There are different chemical routes used to produce branched polymers in an industrial setting. The particular reaction chemistry, and the reactor type and conditions, have a large effect on the number and distribution of branches throughout the polymer molecules. Current research is examining this relationship between reaction chemistry and branched polymer architecture with a view towards the reaction design for polymer melts with tailored flow properties.
more....
Polymer dynamics and neutron scattering
Daniel Read
It is important to understand the shapes, or conformations that polymers
take under flow conditions. Although polymer rheology (the stress response
of the fluid) is one way of probing this, it is important to have other
independent tools to check that the theory is right. A more direct measure
of polymer shape is obtained via neutron scattering from polymers that are
parially labelled with deuterium. We aim to predict neutron scattering patterns
from deformed polymer melts. more....
Suspension mechanics
Oliver HarlenAnother important class of non-Newtonian fluids is suspensions of solid particles, such as spheres and fibres, or droplets or bubbles in Newtonian or non-Newtonian fluids. For example, short glass and carbon fibres are often added to injection moulded plastics to reduce cost and to improve the mechanical or thermal properties of the finished product. Small spheres are often suspended in a fluid in order to transport, for example, pharmaceutical powders around processing plants; and many food-stuffs and skin-care products are formed from oil-in-water emulsions. While the motion of single particles in Newtonian fluids is well understood, suspensions of large numbers of particles that interact through the fluid remain challenging, both analytically and numerically. Our current research includes investigations of how rough particle surfaces can affect the flow of a suspension of solid spheres; how collisions between fibres affect the flow properties of concentrated fibre suspensions; propagation of sound waves through colloidal suspensions; and how droplets deform in a polymeric fluid flow.