What is Rheology?
Rheology is the study of the mechanical properties of condensed matter and in particular complex fluids. The name derives from the greek work “rheo” which means “to flow”. A solid will usually respond to a stress force by deforming and storing energy elastically. A liquid, however, will flow and dissipate energy continuously in viscous losses. A Newtonian liquid has a linear relationship between the shear rate and stress. Complex fluids are interesting because they exhibit both an elastic and viscous response and exhibit a non-linear relationship between the shear rate and strain.
The non-linear mechanical properties of complex fluids are attributed to changes in the organisation of the molecules that comprise the fluid as they experience a deforming force. These changes can range from fast Brownian motions (ps to ns) of smaller molecules and molecular segment rotations, to slower (ms to s) reorientation or reorganisation of macromolecules or large assemblies of molecules.
What is Rheo-NMR?
Rheo-NMR is the study of Rheology using NMR methods and techniques. Rheo-NMR describes a wide range of Nuclear Magnetic Resonance (NMR) methods used to measure the rheological properties of matter.
Two talks given by Paul Callaghan about Rheo-NMR are available online. The talks were kindly made available by the Kavli Institute for Theoretical Physics. The talks can be found at the following links:
- What Can NMR Tell Us About Shear Banding and Ordering
- NMR Measurements of Orientation in Flowing Entangled Polymers
More information on Rheo-NMR can be found at www.rheo-nmr.com.
Some useful Rheo-NMR publications include:
- H. A. Barnes, J. J. Hutton and K. Walters, ‘An Introduction to Rheology’, Elsevier: Amsterdam, 1989.
- G. G. Fuller, ‘Optical Rheometry of Complex Fluids’, Clarendon Press: Oxford, 1995.
- P. T. Callaghan, Rep. Prog. Phys., 1999, 62 , 599.