Neutron Spin Echo for the Exploration of Large Scale Macromolecular Dynamics

Abstract

In soft materials the structures, the macroscopic mechanical and rheological properties and the phase changes are determined to high degree but thermal motion of the atoms and molecules. Most of the relevant dynamics takes place on mesoscopic lengths and time scales in between the picosecond atomic scale and the macroscopic frame. Offering the proper space time observation window, neutron spin echo (NSE) spectroscopy uniquely addresses these motions. In this short review we briefly present some key experimental results on the mesoscopic dynamics of polymer systems. We address 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 of entangled chains. Very recently it became also possible to directly identify large scale internal dynamics of proteins by neutron spin echo. We report the results of these pioneering studies, which most likely will initi...