Traditional physical picture suggests that solvent friction ultimately defines molecular motions and all major relaxation processes in a liquid should be coupled and follow the same temperature variations. Experimental studies, however, reveal strong decoupling (different temperature dependence) in rotational and translational motions in molecular liquids, decoupling of chain relaxation and more local segmental dynamics in polymers, decoupling of protein activity from the solvent viscosity. We present an analysis of various decoupling phenomena, from small molecular liquids, to polymer melts and proteins in solutions. We demonstrate that the decoupling in dynamics of so different materials has a general behavior and is stronger in more fragile systems (systems with steeper temperature dependence of structural relaxation). We ascribe the decoupling phenomena to dynamic heterogeneities on the nanometer scale that affect significantly structural relaxation, but are averaged out on time- and length- scales of other processes (e.g. diffusion, chain dynamics, protein relaxation).

Decoupling phenomena in dynamics of soft matter

244th National Meeting (2012)

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