(79h) Fluctuation-Induced Coil-to-Stretch Transition of Tethered Polymer Chains In Travelling Wave Electric Fields

Electrophoretic stretching of an end-tethered polymer chain in travelling wave electric fields and the associated conformational kinetics due to fluctuations are examined. With the aid of a simple dumbbell model and Brownian dynamics simulations, we show that if fluctuations are small or absent, the chain can be pulled by asymmetric strokes generated by a traveling wave field and exhibit an extension in the field’s propagation direction. It is the first demonstration that stretch of a polymer chain can be realized by time periodic fields with zero mean, as opposed to the usual situations in purely oscillatory fields. The corresponding free energy landscape looks like a vibrating harmonic oscillator with multiple wells whose depths gradually decrease as climbing up the elastic uphill. In this peculiar landscape, even though increasing the wave speed tends to damp stretch, the effect might help the chain keep extended without returning to the coiled state if fluctuations are sufficiently large but not too large to make the barrier crossing time shorter than the oscillation period. In other words, the coil-to-stretch transition can be expedited in the sense that a travelling wave field, in addition to driving the stretching, acts to produce colored noises to lock the chain into the stretched state at a higher energy level. How barrier crossing occurs so as to determine the coil-stretch transition in this vibrating multi-well landscape is also discussed by inspecting the probability flow in the context of the Smoluchowski equation under the Arrhenius-Kramers framework.