Polymer dynamics: From synthetic polymers to proteins

Abstract

In polymeric materials, the structures, the macroscopic mechanical and rheological properties, and the phase changes are determined to a high degree by thermal motion of the atoms and molecules. Most of the relevant dynamics take place on mesoscopic lengths and timescales in between the picosecond atomic scale and the macroscopic frame. Offering the proper space-time observation window, neutron spin echo spectroscopy uniquely addresses these motions. We briefly present some key experimental results on the mesoscopic dynamics of polymer systems. We address briefly the standard model of polymer motion, the Rouse model, the role of topological confinement as expressed in the reptation model and, finally, processes limiting the confinement - we discuss contour length fluctuations and constraint release of entangled chains. Very recently it also became possible to directly identify large-scale internal dynamics of proteins by neutron spin echo. We report the results of these pioneering studies, which are most likely to initiate further experiments on the large-scale motions of proteins and their relation to protein function. © International Union of Crystallography 2007.