Abstract
Thermal diffusion of high polymers in a continuous medium is independent of the molecular weight . Accounting for the solvent molecular structure and the Brownian motion of the solute, we derive an additional contribution of opposite sign which is significant for short chains but vanishes as . Our findings explain the dependence on observed recently for polystyrene, and its inverse Soret effect at very small . Moreover, they bridge the gap between the macroscopic hydrodynamics description for large solutes and the enthalpy-of-transport picture for small molecules.
- Received 2 October 2008
DOI:https://doi.org/10.1103/PhysRevLett.102.078302
©2009 American Physical Society