(455c) Investigating Polymer Relaxation in Nanochannels and Nanoslits

We investigate polymer relaxation in nanoslits and nanochannels with the lattice Boltzmann-Brownian dynamics (LB-BD) method.  Classical theories of deGennes and Odijk predict a transition of polymer properties as the confinement height H becomes smaller than the polymer persistence length, at which the confinement strongly affects the stiffness and restricts the conformational entropy of a semi-flexible polymer such as DNA. With LB-BD, the stretch relaxation time and fluctuation correlation decay time (tr) are measured in nano-confinements of height H, from H larger than the polymer radius of gyration Rg to smaller than the polymer persistence length P. A clear transition in tr is observed for chains in nanochannels.  tr is found to have a non-monotonic dependence on H, as found in previous experimental observations [1].  In contrast, a clear transition is not observed for chains in nanoslits [2,3].  The difference between nanoslits and nanochannels may be attributed to the confinement-induced changes on chain relaxation mechanisms. Hydrodynamic interactions are found to influence the chain relaxation time, even in confinement smaller than P.

[1] W. Reisner et al., Physical Review Letters 94, 196101 (2005).

[2] PK Lin et al., Macromolecules 45, 2920 (2012).

[3] J. Tang et al., Macromolecules 43, 4368 (2010).